Jet is annoying!!!

I have an account with Jet stores, since last September the have been calling me to ask me for payment, which I did monthly without fail as per agreement, my issue is you will be called by 6 different people for the same thing as if they are trying to catch you out or something, the have now handed my account over and the keep sending me messages at night to say I need to pay, I just don't get them, their service is pathetic and irritating, What is the point of making aa arrangement if you still get harassed with calls and messages!!! nxa