Afrihost not being able to cancel your subscription and this is how thy lock you in. its like a invisible contract

I cancelled my Afrihost Fibre in April 2018, I send them a letter stating that I like to cancel my fibre that was on a month to month no contract. The reason for the cancellation is that I have to move from Centurion to Midrand, President Park. There is no Fibre in the aria so no use trying to keep the fibre. I move out the end of April 2018 I did not have access internet access until June 2018, there was a big surprise for me in my internet mail box, I have to pay Afrihost R2975.00. After some arguments with Afrihost and refusing to accept my cancellation letter that was send on the 1st of April 2018. Now they stating that I need to cancel this serves on my Afrihost logon, sorry but this was never indicated to me or any instruction stating that I need to do that, but yet I have not used this serves sins end of April 2018 now stating I need to pay for March, April and May. Is this the way Afrihost do business, It has always been the right why to cancel a serves is to provide them with a letter, now you get ****med in doing thing so they can lock you and not being able to cancel your serves.