Telkom LTE

Telkom LTE service has been below substandard the past 3 month... Not even 1MB on a 10MB service... Logged calls.. No response.. Messenger Telkom support on FB.. They will come back and ask if the service is OK.... Have done something to ask that question.. If so it is a recurring fault... At what stage can I legally say Telkom is not living up to the contract that I can cancel... Maybe they shouldn't have given the network to the Chinese