Rain is a ****

I cancelled my service with Rain in March 2023 and how I'm getting calls from debt collectors for a amount over R2000. I cancelled with them ,they advised that the router would need to be return and they processed this and telephonically confirmed this . I moved to a new provided and have been using them ever since. Months later i received emails in regards to the collection of the router ,which was collected and i received confirmation . My question is if this PREPAID service was cut and cancelled in March of 2023, is it possible to incur over R2000 in data usage . Especially if the router is unplugged in a drawer and I am using a different provider.