International roaming - NOT!!!!

I travel abroad regularly for work and EVERY SINGLE TIME i am stranded internationally being cut-off from networks even though I activate roaming on the app and call the customer care ahead of time to ensure all is in order. I can understand that maybe in 1 or 2 countries there may not be roaming agreements but it cannot be that in Dubai, Germany, Poland, Spain, Amsterdam, Portugal just to name a few - there is nothing! I am highly frustrated this week yet again having to purchase prepaid sims because my international roaming does not work - not just on 1 but on both of my MTN numbers. What a joke this company is!