Question about Paying of CC Balance w/ Credits

I have a quick question, don't know if anyone has the answer to it.
I currently have TDCT Credit card if it matters.

Let's say my January Bill is $1,000.00 and I want to pay it all off without incurring interest.
If I receive a $500 Credit (for a return, or something else) I only have to $500 to reduce my balance.

However, lets say my January Bill is $1,000.00.
I then purchase an item for $500.00 in February, but return it the following day. My account shows a $500 credit on my account.
Can I pay only $500 in January (because I have the $500 Credit and the system shows that I technically received a $500 Credit, and then I pay the other $500 in March) or do I still need to pay the full $1,000 in cash (not using the Credit).

Just curious, my December Bill got completed screwed up with so many credits, that it's tough to keep track. 

Yes it should work. Credit cards can give you an infinite free loan of at least half your credit limit. With RBC, after my statement has been issued, I've booked a refundable hotel room or airline ticket for the amount owing on the statement then canceled it the next day. The credit would count as a payment, and the original amount would be payable again next month. If you do this over and over each month, you can put off having to pay off your card without incurring interest charges. The bank reports you as having paid on time, and I never received a complaint from them about it. It's only a hassle of booking and canceling each month.