Change of plan nightmare

I requested to change my plan in December 2022. However, nowhere in the information received did it stipulate that this plan only allowed me to use service providers from a specific network. Once aware of this I immediately requested an upgrade to the Classic Saver plan on 4th Jan 2023. Discovery declined my request although it was sent only three days after the cut-off and no services were used from the plan. My broker has escalated the matter but Discovery is causing further delays (a week now) when the matter could have been resolved. Very very disappointed with the service received. There is no culture of care at Discovery. As a loyal customer for more than six years who has barely used the services, they could at least be reasonable and approve my request.