Telkom takes 100GB with SIM card removed

I have been experiencing an odd issue (as **** to be frank) with my Telkom mobile line since around March this year. At the beginning of each month, on the 1st, Telkom takes over 100GB of my data.

Today (1st of Sept), with my router unplugged and SIM removed, Telkom says I have already used 126GB. And this has been the story for months.

When I get in touch with Telkom to resolve the issue agents say the Telkom is always accurate and that I must monitor my data usage.

Absolute *******.