DStv Reneging on Offer after Acceptance

We received an email on 10 July with an offer to reconnect our DStv account for R520 per month for 3 months, provided that the offer was accepted by 31 July. We did so on 13 July, paying a pro rata amount of R240 - given that we were half way through the month. This was done through the "Reconnect Now" button on the email offer and paying the amount displayed. On attempting to connect for the second month last week, the amount to pay was R790 - the full amount. We did not pay this, with the intention to contact DStv to resolve the discrepancy. We assumed that this would run to 31 July before renewal however, received a disconnection message today. We then again, attempted to pay for month 2 - but the amount remained at R790. On phoning the call centre, agent 1 was only able to say "the offer was removed". We then requested a supervisor who could assist and were transferred to agent 2 - Mavis. Mavis firstly told us that we had waited to accept the offer and it was now the end of month 3 because it expires on July 31. We forwarded the email which reflects the sending date of 10 July. She then proceeded to tell us that it expires on 31 July, so do we expect DStv to extend the offer just for us. We attempted to explain the basics of contract law to her at which we were told we were insulting her intelligence. The point we were trying to make was that the offer expires on 31 July rather than the 3 month period. She could not grasp the difference between the acceptance of the offer and the end of the 3 month period. She also told us we need to read the terms and conditions - which we had done prior to contacting the call centre. Point 2 in this documents reads: "2. The residential customers, who reconnect by 31 July 2024, will be charged a discounted R520pm for 3 months." We therefore should be entitled to a second and third month at R520 each. Please could this be rectified urgently. In addition, your call centre staff were extremely unhelpful, condescending and rude. There is clearly training required here.