Unilateral change in Contract parameters - Night Express data time changed to 05:00 from 06:00

I signed up for a data contract during the latter half of 2019 due to the good value of the contract and the 20 Gigs of night time data that can be used until 06:00 in the morning. I have recently discovered that MTN has now changed this time from 1December 2019 to 05:00 without any notification to Customers. Based on the key parameters of the contract that I app**** for (and which it was sold to me vs. the competition), the usability of the night time data was a key consideration and also a key contractual parameter to the contract. Changing the time parameter is as good as changing the amount of promotional data to the contract after signing a customer. I logged a customer service request on the 8'th of Jan 2020 to resolve this issue and change this parameter back on my contract to the Contracted parameter time of 06:00. This service request has been bouncing around from person to person and department to department without any action. Requests to be updated and contacted by the Customer Service manager has been in vain.

I view this as a change in the fundamental parameters of the contract and now reserve the right to cancel the contract at any point during the contract period.