Sim swap for prepaid number

I ported my vodacom number to telkom 3 years ago and I recently visited Telkom store in Hatfield Pretoria and a lady told me she can't do a Sim swap for me because I also have an account with them which is currently in arrears but I am paying monthly for it. What has my prepaid number got to do with my account??? I don't understand why telkom is doing this. I am so disappointed I will port back my number to vodacom.