Catch you with special tariffs

I took up a 12 month contract with MWeb in December 2022 after I accepted there quote I received with a email for the amount of R509 per month for a 50 mbps Fibre. By receiving January invoice to find they invoiced me for R689 I spent hours on phone with there accounts department with no success except promises to sort it out now I received invoice for February still for the amount of R689 with more promises. Seems they catch you with promotional specials but don't honor it and after you receive your instalation they charge you not what you was quoted.