I have a fixed mobile account with Telkom since 11 December 2021, the deal was fixed at R269 per month on services of home router

I have a fixed mobile account with Telkom since 11 December 2021, the deal was fixed at R269 per month on services of home router. I am surprised that they increased the contract to R279 this month without even telling me whats the reason for the increase by R10.