Tony Hetherington is Financial Mail on Sunday's ace investigator, fighting readers corners, revealing the truth that lies behind closed doors and winning victories for those who have been left out-of-pocket. Find out how to contact him below. 

D.N. writes: My wife and I booked with Tui to go on a five-day 'Mistletoe & Rhine' cruise, starting on November 23 and visiting a Christmas fair each day in five different German towns and cities. 

Now I have just been informed that the first fair in Frankfurt will not even have begun when we are there, and the fair in Koblenz will be closed for the 'Sunday of the Dead'. 

Tony Hetherington replies: The Germans stage great Christmas fairs and markets, and you were promised five of them as the Tui Isla cruise ship travelled the Rhine.

Then Tui dropped its bombshell. On the first day of the cruise you were supposed to visit the Frankfurt fair, but Tui explained it would not begin until two days later, on November 25. And Sunday, November 24, is 'Totensonn tag', a public holiday when people remember those who have passed away, so the Koblenz fair will be closed.

Tui explained: 'We plan our itineraries a long way in advance of the actual sailing date using information available to us at the time. Sometimes we find we need to update you as more information becomes available to us.'

Really? Christmas fair dates are known a year in advance, and Totensonntag dates are already known through to 2034.

So how long ago did Tui decide its sailing dates? And what unpredictable new information fell into its lap a few weeks ago that made it realise it had promised its passengers the impossible – two fairs that simply won't exist while its ship is at those towns.

In fact, all this has an air of panic about it. Three days after Tui contacted you with its bad news, I found it was still advertising your cruise with the promise of five fairs in five days. And as I write this, I see that the independent online agent Crui.se is still offering Tui's trip to the non-existent Frankfurt fair on November 23, and the closed Koblenz fair the next day.

Not to worry though. Tui assured you: 'Our onboard team will have a programme of activities and entertainment for you to enjoy on the ship.'

Well, if I were a passenger who had paid the £1,997 you and your wife forked out, it would take a lot more than the sight of the ship's captain dressed as Kris Kringle – the German Santa – to make me forget that Tui has scrapped 40 per cent of the attractions it advertised.

And the huge irony in this is that Tui is a German business. That's right – the Germans forgot to look in their diaries for the Sunday of the Dead and forgot to Google the dates of their own Christmas fairs. You have to wonder who at their Hanover HQ suddenly realised this late last month and drafted the letter you received, in which the word 'sorry' appears nowhere at all, just like the word 'refund'.

Now, you might think a refund would be offered automatically. Well, not by Tui. It told you the changes were minimal, so there would be no refund. Not surprisingly, you cancelled your booking. You have told me that Tui refunded only £599, keeping the balance as a cancellation charge.

Frankly, I think Tui has committed a breach of contract. I asked Tui to say exactly when it discovered that the Frankfurt and Koblenz fairs would not be open. And I invited Tui to explain why a loss of 40 per cent of the attractions it advertised should be regarded as 'minimal'.

Tui asked for time to respond, and we agreed the company would comment by last Tuesday. But when Tuesday arrived, it asked for a further delay to consult its lawyers. I refused, and Tui finally offered this: 'We would like to apologise to customers impacted by the change to the Christmas market sailing on Tui Isla's 'Mistletoe & Rhine' river cruise on November 23. We are currently investigating the impact with our team, exploring options, and will be in direct contact with our customer.'

No answers then, and no explanations. So Tui, I will be returning to this and reporting again when you have finished investigating and exploring. Your customers deserve better.

British Gas demanded £5,211 – for a £135 bill 

Ms L.B. writes: We received a ludicrous bill for £5,211 from British Gas, showing the meter had risen from 4973 to an estimated 5043, but the figure on the meter was only 2989.

Tony Hetherington replies: Receiving a dodgy demand is bad enough, but your problems were just beginning.

You rang British Gas and were assured the next bill would put things right. Instead you received another two demands for £5,211. You submitted a complaint, complete with a picture of the meter reading, and British Gas slashed your bill from £5,211 to £135!

As soon as the revised bill arrived, you went straight to the post office and paid in full. But the next day another letter arrived, telling you that the £135 demanded just 24 hours earlier was now outstanding, and threatening legal action.

Then two more letters arrived, both telling you that your earlier complaint had been resolved. Excellent – except that a fortnight later yet another letter said British Gas had called in debt collectors!

I questioned British Gas and it told me it had never heard of you – that all its bills went to 'The Occupier' at your address. It denied issuing any payment reminders. You explained that you own the house jointly with your sister, and had never bothered to put one name on the account. But you certainly received reminders, and you gave me copies.

Finally British Gas admitted the cause of the entire problem was incorrect figures noted by a meter reader. It told me: 'We are sorry for the error. This has now been resolved.'

But I do wonder why nobody at British Gas could have taken responsibility for sorting this out much earlier.

If you believe you are the victim of financial wrongdoing, write to Tony Hetherington at Financial Mail, 9 Derry Street, London W8 5HY or email [email protected]. Because of the high volume of enquiries, personal replies cannot be given. Please send only copies of original documents, which we regret cannot be returned.