This literally happened to me recently. Was going to Germany for 2 weeks and wanted to use a cheap eSIM for data only. I asked them if they could unlock my phone so I could do this, and they said no since it’s not paid off. I still have a new months left to pay it off, and didn’t wanna drop $250 to do that so I just had to pay the international data plan. $12(maybe $10? Can’t remember) a day, 10 day maximum charge per cycle so I’ll pay $120 for mine and $60 for my partners. Instead of the $11 30gb data plan I wanted. I’m never buying a phone from a carrier again, I will always just buy it outright from now on. It was a stupid situation.
Also the data roaming sucked, each time we moved from one provider network to another we had to restart our phones as the data didn’t wanna work…