Important boost mobile over billing question!!!?

alright, I went to boost mobiles website to buy the galaxy s2, I put in my credit card information and it was supposed to come to 350 something (promo code made it cheaper) and the problem is, it came up with a boost mobile error page saying something was wrong with my credit card, so i tried it a couple more times and still wouldn't work, and now on my bank account i'm being billed 5 times for the same phone... what can I do to correct this? i don't even have that much money in my account, just a little more than the cost of the phone is available... I'm pretty upset about all this.. how do I correct this before I get an overdraft fee for being charged too much money.. If i call boost mobile can they cancel the billing for all but one of them and it go back to normal?? need an answer right away