shocking online service

Disgusting online service. I paid for goods without realising I needed to do a bank transfer at a later date. I then received an email a few weeks later saying I have to pay a penalty charge late fee, and that I now have a bad credit debt....all for the sake of £38. The funny thing is, I didn't receive any late notice warning beforehand. Once I found out I tried to call them and pay over the phone, but they wouldn't accept any payment. They said I had to set up a direct debit with my bank. The customer service team do not want to help either with this matter. Do not buy from this company online. They are despicable.