Unhappy customer

Last year we ordered online via vodacom app two tablets. They delivered three weeks after the order not two tablets but two Sim card's wich we phoned and said we did not order. Three months later they collected the sim cards and said it was cancelled seeing that it was not what we ordered. Last week when we wanted to get two cellphone's on contract it was declined because of an a rear account of R800. When we called and explained that those sim cards was the wrong order,cancelled and collected and that we now have a bad name and cannot get contracts they said we must pay the amount first ...we are not happy with that and feel that we don't have to pay for something that we did not order and did cancel and has been collected last year. We need phone's for work but because of vodacom's bad service and own negligence we can't get it and they refuse to give service.