Overcharged when cancelling the contract

After being a client for more than 8 years I am relocatting and needed to terminate my service. According to the Home-Connect service terms https://home-connect.co.za/terms/ I needed to give 1 calendar months notice on their portal, clauses 11.3 and 11.4 and "Either Party may terminate the Agreement (or the relevant Service Order): You may terminate the Service Order at any time by giving Home Connect 1 FULL calendar months’ notice (not 30 days), defined as per clause 1.26. All cancellations must be processed via the Home Connect online portal using your login credentials: https://portal.home-connect.co.za." . Checking Clause 1.26 "Calendar Month: means the period beginning on and including the first of each calendar month and ending on and including the last day of such calendar month. " - On Saturday the 1 March I therefore logged onto the portal to give 1 Calendars month notice. Imagine my surprise when the only termination date I could select was 1 May. I wrote a strongly worded comment and waiting for them to call me on Monday. I was called but was informed that a calendar months notice was from the day before the 1st of the month and not on the 1st of the month and if I did not transfer my service to my new address, I would be charged for April as well. No amount of discussion could change that. I am going to seek legal advice on the matter as I have a large contract and its a fair amount of money to throw away.