I sent a letter to the landlord stating that I will be trying to find a prospect for subletting. In Canada, the landlord has 7 days to respond or the tenant can file a 30 days termination notice. 7 days passed with no responses so I sent the landlord a 30 days notice. The landlord responded 2 days later saying that they received no such letter asking to sublet and that I am still responsible for the one month remaining on the lease. How can I argue that they in fact recieved the letter and are back peddling now because they did not respond in time?