Telkom Mobile very bad Service

I had a telkom mobile account in 2015 but I closed it in 2015, they called me beginning of May saying I'm owing R54600 I paid the account on the 12th of April 2018, they promised to send a paid up letter in 48 hours and when I call no one is willing to help me get my paid up letter, they all say the letter comes from a different credit department , the agents are rude, some even hang up on me.