Cancellation of unlimited plan from 2021

I received a letter from O2 stating that they will not allow me to continue to have the existing plan and therefore was cancelling my service, unless I changed to another plan. It seems that the optimised plan is cheaper but does not cover the unlimited plan that I have. As upgrade I am not allowed to select unilmited plans anymore for my number. I can get a different phone number but I can't make my plan unlimited. Contractually they have to provide 20 years of plan security, although I am month to month, I am willing to sign another 24 month plan. I also added another line for my Child and my spouse. But they won't let me get my spouse a line. I pay over 1K a year in services to O2 but they decided I am not valuable enough. No explanation, just cancelling my order. I pay my bills and have no issues with my bank and I live in Germany but still o2 wants me to take my business somewhere else. I have been with O2 for over 10 years. I just wanted to know if anyone else is being discriminated against or not allowed to get additional services. My average use is 500GB total which is not abusive.