Is this even legal in the state of tennessee?

Ok, i owe some money to a credit card company. i setteled on a deal but one month i couldnt pay so i asked if i could send the payment a little late they said no and rudely hung up, so i never sent that payment. Today i got a letter saying basically that they took all my money in my account at the bank and all money that goes into my account will be differed to them and my account has been frozen. i never received a warrent or even a summons. is this robbery or completely legal