Why is it the customer's responsibility to provide customer care sevice?

Terrible service. Took out a contract via MTN. Followed up with Customer Care throughout. They sent me in circles. Called Mondo today and they said the contact was cancelled due to availability. I then asked why did no one contact me to tell me this, and they said it's the customer's responsibility to contact them within 7 days, which I did via email, no one got back to me once I submitted my documents. So I have been waiting with no communication, thinking my phone will be delivered, but nothing was coming. Honestly frustrating and terrible service.