Hathway — Executive calling to return router even when it had been left at location and informed

Hi Due to to covid I had to relocate to my native place so I need to disconnect Hathway connection last year. I had cleared all dues and asked the person who had installed it to take router from the house. After 1 year they are again calling me to submit the router. It's really annoying. If these type of call continues then I need to lodge complaint against Hathway.

Let me know what to do. Sometime they call to initiate the connection again. Sometime they tell me to come to that location and many thing. Please let me know what to do now. I tried to block the phone numbers but they keep calling by different number. They are really behaving like GUNDAS. I suggest everybody to not take any connection from Hathway and especially the local Hathway provider. They promise that their will not be any problem but now he had not submitted the device (I really don't know) because of which I am getting useless calls. Please help.