income support lost my forms?

hi all.
when my partner moved in, i called income support to inform them, they told me they would send me the forms in the post and when completed to take in to our local benefit office.
we did so, handed them in by hand.
4 weeks later, we hadnt heard from them, so i thought i best chase the claim.
they told me nothing was on the system, when i explained, they told me that forms often 'get misplaced' and this is why its all mostly done over the telephone or online. so we did the new..new claim there and then. over the phone.
when we got the letter 3 weeks later with the payment from date. it was awarded from when i applied online.
i asked them what i could do as they lost my form. they were unsure and said they would ring me back in the next 2 days. this was 4 weeks ago. i called them a week later. to be told the same thing. i have googled it trying to find out if it happens a lot. and how to go about it. but i cant find anything.
has this ever happened to anyone before?
or does anyone have any advice please as to who i can call, who can actually help?
thankyou kindly xx