Sure you can. And it's extremely easy:
1. Start the normal purchase procedure, specifying that you're going to pay with a credit card. (Don't worry, you will change the option later on in our payment gateway).
2. Go on finalizing the procedure: once you are transferred to Avangate, select the third button "Wire Transfer".
3. You will then get the instructions about how to proceed. Remember that being a wire transfer, the payment will not be processed immediately: hence to get your turboSMTP new credit you must wait around 3 days (it's what it normally takes a bank to process the operation).