One missed payment then given over to debt collectors

I have been a loyal customer of Vodacom for years and have been paying diligently. In March due to the delay of the UIF payment, they could not deduct an amount of R158 from my account as a result they handed me over to a debt collector without even sending me a letter or making contact. They are the very worst and I would never recommend their services. The worse yet is that I don't even use the Sim and have been advised by my husband years ago to just cancel the Sim. But now ofcourse that is first on my list.