Job Centre didn't notify me of full details of part-time work????!!!?

Well I'm stuck in a bit of a pickle. I have started working part-time for a retail company and I checked all out with jobcentre, they told me I could not do over 16 hours and so my benefits would not be affected which is okay because my company wouldn't offer any full-time.

I filled in a part-time working form and found out while signing on I have to also give in another sheet every signing on date (every fortnight) including any additional money plus pay wages. But that was OK because I am very organised so I wasn't all muddled up.

However I get paid once a month and I discovered that I was paid £20 less than my usual on benefits. I received a letter, telling me because there's a change in income, I am not recieving less. However I checked with the woman beforehand and she told me, plus the interviewer with my company AND also my job agency that I am with, directed by the Job centre that my benefits WOULD NOT be affected If I took out part-time work.

I went to the jobcentre and spoke to adviser about it. He said because I only get paid once a month, they will deduct my money once a month and If/I lose any money they will deduct it on that day. I asked him why the money was deducted (they always make mistakes and having lost over £200 money before to the jobcentre on two occasions, but received one amount back), he told me it was because now I'm working part-time, Job centre automatically deducts my first £5.00 earned if I worked part-time, I did 3 shifts that month and I lost £15.00, he told me I would have been notified before I filled in the form. I was not. He told me a member of staff anyway would have notified me, They did not. I walked in when I was free one day and picked up the form, filled it at home then popped it back.

He told me he would contact his area manager and call me Monday. He did not. I am not happy at all I lost my £15.00, in fact I lost £20.00, I printed a bank statement and it told me by the figures I have lost £20.00 not £15.00. I know this is not a HUGE amount but it means I did my one shift (which is only £40 a shift, bear in mind at least £10 petrol!) for nothing. They did not notify me, and he tried to go further on that Friday by even calling me a LIAR.

I am going to go there again tomorrow to see about this. The letter by the way said nothing at all about an agreement and neither did the form. He told me neither would because I had to find out either by a member of staff or by a seperate brochure, which he couldn't even find on the Friday!! I told him I want to overlook the opinion, (it said on letter to contact within 3 months if I'm unhappy about this change) but he refused to give me a form to be able to do that.

I was wondering legally of course, where can I go from this? Can I get my £20.00 back if I am able to prove I was not told?

I can GUARANTEE my signature was not signed on ANY part that allowed them to take £5.00 from every shift. I EVEN asked the worker at the time, i would NOT do part-time work if it costed me anything, and would prefer to risk doing full-time work with them instead for the sake of any money possible lost.

Sorry it's so long, thanks in advance for any help/advice.