Horrible service from Cybersmart

Cybersmart ran a promotion where they doubled the fibre speed for 3 months at no charge. I had to decide during this time whether I want to keep the new package or not. I had to inform them before end January 2023 if I did not want to keep the new package and they would downgrade my package to the one I had. On 11 January 2023, I informed them via e-mail, as requested, that I do not want to keep the new package. The sent me my bill for February, indicating the new package. I rep**** to them and also phoned them about them about it. I paid the normal amount plus R100 (some handling fee if I don't want the new package). A few days later I received a statement from them, informing me that I am overdue. I phoned them again and the lady I spoke to promised that they will sort it out and that a manager will phone be back. Nothing happened. Today I received yet another statement that I am overdue and the e-mail from them has taken on a threatening tone. Now I am wondering if it is not maybe time to switch service providers. I can see why they are not the top ranked ISP in South Africa any more.