They may not be much better but you can least speak to a human or find contact emails for someone who will eventually escalate things. Maybe Melon is a bit better I don't know but lots of these Mvno's run on skeleton staff and even speaking to anyone via any channel can be neigh impossible. The scum of the earth the Ignition group runs 2 or 3 of these Mvno's, I have had dealings with them previously and they are totally useless, their sole purpose is to take your money and then drop you.
The only Mnvo that may be ok is Afrihost and even there I had a terrible experience with their support, it took 4 weeks to do an esim swop, their support incl the rep on the forum are as dense and slowed up as you could possibly imagine. During the whole time I could not use the number, imagine if that was my main number
Despite how bad MTN can be I've never had any down time with my numbers in all the years I've used them, I've had missing airtime and issues with contract billing but the sims have always been available and sim swops seamless.