Mortgage interest error - Help Please!

MWT

https://forums.moneysavingexpert.com/discussion/comment/81873428#Comment_81873428

For the rest of us, we pay what the lender asks and assume it is correct. Particularly after a complaint was upheld, the first thing I would expect the lender to do is check you understand what you are paying going forward.

I've never trusted any lender without checking the numbers, and if I'd had a complaint upheld the very first thing I'd be checking the following month was that the upheld complaint had been properly implemented…

Either way, the OP is where they are now and to some extent how they got here is less relevant than dealing with the situation they are now in…

If it had been converted to fully repayment then they would have had to pay more than they have paid with it remaining as IO, so it is not so much a matter of the wrong interest being applied, it is the absence of them being charged for the capital repayment part each month, so one can only hope that the IO element is not large…