MTN service stinks - once again!

So, here I am trying to sort out another MTN account! First it was my son's contract, now it is my mother's account. She is 80 years old and a pensioner. End Jan18 I helped her to upgrade her package to the R289 per month deal, no device. She still has a very old Nokia phone, and doesn't use any data. Just calls and sms. From end Feb she has been debited with over R300 per month - NOT R289!!!. I went back to the Herm**** store end March 2018, they said her sms's weren't discounted. She will get get a refund. Guess what? We are at May18. She has this morning received an sms from Yello: Thank you for your R415 payment!!! After they told me it would be fixed, it wasn't. I phoned the store again and they promised to investigate and get back to me - I am still waiting after about a month. Today she pays R415. She is a PENSIONER!!! She cannot afford this! And now you are going to phone her, and she is not going to know what is going on! My next move: As soon as this contract is done (unfortunately only in 18 months), I am moving my mother over to Vodacom as well - like I have done with my son's account. NO hassles, NO problems! Don't even try to phone the call centre. If they tell you they will log a query, you are going to on pension before it is sorted out.