Overcharging dstv compact from R399 to R479

Dstv is overcharging. I'm a compact subscriber and every month I'm paying R399. Today I received an sms from multichoice that I must pay R479 before 31 of May 2020.

This is day light ******* and worse part, you can't even communicate with them over the phone as I can't get through. Even there ussd and whatsapp self-service platform is useless as it is only cater for account upgrades and downgrades, tv errors, payments, insurance, but there is no option where you interact with someone.

I need explanation why I've been overcharged as a customer.