Hmrc what they hell?!

[ahhhhhhhhh]

We were overplayed last year and have a nearly £4000 overpayment.
Not ideal but fine, since October I have tried and tried to set up a payment plan which they won't accept, I refused to do Income and expenditure over the phone and requested to send one. this was accepted (recorded phone call proof) and was delivered to them via special delivery in December.
Rung up today to find out what was going on to find out they changed my husbands income figure for the year to £12000. This is no where near correct and have started paying us £50 a week tax credits! Money I do not want because I know for a fact we aren't entitled to any money and this is going to spell another overpayment.
How the how can they get it so wrong from an income and expenditure form?! I've now changed the income back but they can't stop the money at moment and won't let me set up a payment plan for the overpayment which I desperately want to do. They are aggressive rude, unhelpful. Who refuses to take your money and then gives you more?? For fucks sake. The stress of this is making me ill!
Nothing they can do apparently I think those were the only words she knew.

Is it from tax credits? They kept 6 months worth of money from me for over a year, even though they accepted that I was entitled to it.

If you haven't done so already, contact your MP. They can get things sorted. (Nice man from my MPs office just sorted out a problem with my local hospital for me. They wouldn't give my son a date for his operation because of an admin error, but they weren't allowed to talk to me about it so couldn't correct the error! It took him one phone call and suddenly it was all sorted.)