Courier Guy dishonesty and unprofessional

The Courier Guy has made problems for me ,they send emails of me being in arrears and they hold my parcel ,then once I deposit the arrears they say sorry i was not in arrears then i ask for my refund ,then they dont give me back ,instead , they put that money back to my Courier account and the only way I can use the money is to send another parcel . This is exactly how ****s work ,then when I ask for my refund, they threaten to delete my account.