Credit Card

It's the end of the month and it's time to repay my credit card. The last time I made payment via phone banking, the operator told me, there is an offer of 9 months' interest free and he wasn't sure whether mine has that offer. He suggested me to apply another one...so kind of him.
I refused because I can't afford it. I knew I will use both cards without limit and the repayment will be hectic for me. I have heard of students holding several Credit Cards during their Uni's time. Repaying by cards to cards in a circulation. I wonder how this can be happened.