Poor service

I recently moved and i cancelled my service provider .After 2 months i still get billed,although i informed them that i cancelled my account.On the 16 th of february 2021 i get a message that i am be billed in the amount of R1458.00 for a Ont device that went missing.I contacted the owner and he informed me that the device is still there where i left it.My question is how can they say that the device is missing and start billing if they have not contacted me to inquire about the device.Is this how they operate?