I recieved a call from my banker telling me my account is in excessive because they have recieved a debit order from cellc ,I have a contract with cellc new contract I have recieved the phone on the 29 of July,I was advised my 1st payment will be the 27th

I recieved a call from my banker telling me my account is in excessive because they have recieved a debit order from cellc ,I have a contract with cellc new contract I have recieved the phone on the 29 of July,I was advised my 1st payment will be the 27th of August nothing was discussed about the upfront payment at all now I am told I will be charged an extra amount for not paying the upfront payment...whose fault is that...