interest problems

I bought a product from a shop on 4 months interest free credit, I was told that i'd be told of the dates and details of when to pay the amount. A couple of months passed and I noticed that the company had taken 3 payments from me within 4 weeks, after this I decided to pay the remaining loan amount in full, yet the company still wants interest to be paid from day 1.
Firstly, I don't think I should be charged any interest at all due to them not telling me about the dates/details of the payments that I had to make. Secondly, even if they did want to charge me interest it should only be for the amount of time I went over the interest free period and not from day 1 (ie-4 months) as they did.
Can you advise me on what to do please.
Thanks

btw-im in the UK, sorry but this is the only legal message board I could find.

Interest free financing contracts in the US have a provision that if the full balance is not paid by the end of the interest free period, you will be responsible for interest from the date of purchase.

I assume this is the same in the UK, and as such you owe the interest.


[email]JASON@LEGISLATOR.COM[/email]

even though I was not told of the final deadline to pay the whole amount?
thanks for the help