2 A9 tablets stopped working after a month of buying them

I bought 2 Sumsang A9 at CellC with a contract last month. I had a problem with the first one after 2 weeks it was not charging and I send it back to cells c and they said I should pay R3000 to get it fixed while it never fell or anything and again yesterday the other tablet stopped working as well. It had a same problem of not charging. So cell c should take thier phones and cancel my contract if they are not fixing this phones.