Based on this https://forum.lowyat.net/topic/3901318, it is a known issue with 4g lte phones, and based on various post in this forum and others, the way it is handled varies with telcos and even different personnel within the same telco.

I guess the only way to handle this issue is to file complains with telcos, skmm/mcmc, and cfm. Until there is a permanent solution, it is best to turn off 4g lte on the phone or use 3g only phones or just 2g phones when travelling. And must remember to turn off data and roaming.

Edit: Another thread with the same issue: https://forum.lowyat.net/topic/3919502

easier for telcos to charge first, then refund if got complains... no complain, keep the money...