Account Restricted

In the past few weeks, FedEx overcharged me by around $1500 for carrier adjustment which caused my balance to go negative. Amazon attempted to collect that money from my bank but it was declined since i did not have that much in my bank. However, i continued getting more sales and my account balance came back up into positives. Amazon restricted my account for not having a valid card on file. I am not sure what amount they are still trying to collect since i had a positive balance after having new sales. Any suggestions?