MTN Data Package

I have signed a contract on 23/04/2019 - My MTNChoice 1GB for R 109-00/pm. This was advertised in MTN booklet as contract of 2GB day and 2GB night data. From the first data received in May 2019 - I only received 1 GB day/month. I have reported this where I signed the contract - Somerset Mall. It is still not resolved. I am receiving only 1 GB day/month and the contract value is R 114-00. I want to terminate this contract and request MTN to pay me the money back that I payed extra every month for 2 GB and only receiving 1 GB. MTN is now disputing my contract and say I only singed for 1 GB day/month. MTN shouldn't promise 2 GB and call the package 1GB. The staff don't know how to implement this...