Demanding funds for no active service

Last year in September I cancelled my 5g and requested an immediate cancellation. The lady said they only process cancellations at month end and will collect the router then. Which they did. I also asked her if there will be any amounts due and she said "no sir, there will be no further debits as your account is up to date". Every day I get calls from rain asking to send a link so that I can pay them. For what? They collected the router and I am not using their service since September 2025. I have mentioned to all I have spoken to, to rather search for alternative providers because this is how rain operates.