Bad service

I had an Jet account that I recently settled on the 16th of April after months and months of agents from this company calling me non stop regarding the paying. Two days after settling I called to request a Paid up letter, agent who assisted me said they have escalated it to the relevant department. And I should recieve my paid up letter soon. I called again after checking my emails nd was told it was escalated to this certain department. All in the meantime I'm still receiving sms that I need to make an urgent payment to my account. They have been nagging me to pay nd now that I have, they cant provide me with a Paid up letter. This utterly ridiculous I have to spend more money on airtime calling them regarding my letter.