Unsatisfactory service from MrP Mobile

I'm being hounded by MrP mobile after fully paying the account and cancelled the contract on numerous times .Every time I was told it takes 30days to cancel , I've done that .Now after 4 months I'm being hounded saying I still have a outstanding amount .I didn't even when use the sim but paid .I'm frustrated because they handed me over to lawyers .It's extremely, extremely frustrating.Yet when you speak to them they say Al calls are recorded ,so why not go back to July , August and September the months I've been trying to cancel .I was advised the end of September it's paid up and cancelled. So why come after 4 months insisting I owe them money .