Telkom do what they want without you Knowing

Worse service provider, last year Telkom sent their technician to install a new modem, my mum who is a pensioner was at home. They swopped out my ADLS line for a LTE line without me knowing or explaining to me the account holder. I finally got around to calling them to upgrade my line due to working from home, now i get told i cant go higher than 4mb so i told them cancel to which i was told i am in a new 24 month contract. Who explained this to me or where did i sign to agree to this? I pay every month for a product i cannot even use properly. Can a competent person cancel my contract so that i can put in a provider who can give me what i want. We in lockdown my kids have to work online and so do I, i am left hotspot ting my phone because the speeds your offer are ridiculous. Why did you put a useless line that i cannot even upgrade? 4mb per a second you cannot even stream. Stop false advertising as well fix you website it states i can go upto 90mb but when i call in they say highest is 4mb.