I took out an interest free balance transfer cr cd in march for 700., for 15 months interest free and i thought the card was interest free for 20+months for spending as well.

The statements are saying an amount on what to pay to avoid interest, why??

I have pd well over the minimum payment every month since and tesco are charging me interest on the balance. I'm using the card for shopping etc.

I Cannot find out what offer i took up to prove what the agreement was.

Can anyone please point me in the right direction. I've had nothing through the post.
Many thanks