Tax Credits Not returning calls or helping at a dead end

nattod

Hi All
Was just wondering if anyone has been in this postition and if so what did you do!

I rang up to add a child on to my tax credits but he was 3 months old and 5 days, which is over the dead line and was told it would have to be passed onto there head office.
I was told i had to wait upto 14 working days for a response from there head office to say my child had been added if not to ring a number.
I never received my letter so rang the number which is an answer machine you have to leave a message and they will get back to you with in 48 hours. I have rang this number 3 times and have gave them longer then the 48 hours deadline each time, but still nothing this has been going on for 2 months nearly.
I have contacted tax credit main helpline number and i keep getting told there is nothing they can do as its out of there hands.
Ive been told there is no number to talk to anyone just the number ive been ringing, there is no email address and no address to write to them which i find very hard to believe. Im owed nearly £700 which is a lot of money to a single parent.
Can anyone help:(