MTN

In June 2019 I took out a 24 month contract for 1024MB data, 125 minutes and 100 SMS. All went well until May 2020 when the package was reduced to 350MB data, 75 minutes and 50 SMS. I contacted Customer Care. Sent them my contract as requested and then heard nothing until I got an SMS to say problem resolved. At no time was I able to speak to a human being and the problem is not resolved. I went to the main MTN office at Century City where a kind manager tried to help. To date the problem is ongoing and nobody can tell me why my package was reduced. What can I do now?