Can the government take more money than I pay them montly for stafford school loan?

I have been unemployed a whlie due to economy so my stafford school loan has been delinquent and I owe waaaaaaaaaaaay more at this time than I can pay with my new job. They want a lot more monthly than I can pay but I did want to make some payment towards it monthly (lot less than they want). I was wondering if I pay with a debit card online can they take more out than I authorize legally since they will have my account info? If so, is there anyway around this? Thanks!