What if I use all of available credit limit, and then pay everything, then use again before the end of month?

I just started with 300 credit limit.|||You don't say whether you have any interest free days per month. If you have any free days, providing you don't go over yr limit you can re-use. However if there are no interest free days you will have to make allowance for yr purchases plus the interest that has accrued prior to paying the balance.|||You will owe interest on your average daily balance, about $300 x .015 = $4.50