Cost for senders when receiving texts in Belgium on a US or Belgian SIM card

First, my specific question is : How could I receive texts from both US and Belgian phone numbers without the senders paying additional fees? (i.e. on top of their national text plan)

I used to live in Belgium, but haven't visited since before smartphones became so prevalent. I'm hoping someone here might have experience using AT&T's Passport plans for international travel in Europe (and/or using burner phones in Belgium). AT&T offers 3 tiers of "Passport" plans which are good for 30 days, cost a flat rate, and come with an allotment of data. These plans claim to offer unlimited texting. They also provide specific rates for voice calls and data overages.

I am wondering about the texting component. I understand that while in Belgium, using a Passport plan, I can text US numbers and various international numbers for free. What is not clear, however, is what will happen when the local Belgians or my contacts back in America try to text me.

I did one of those help chats on the AT&T site. I don't fully trust those things because I've been told wrong information by chat agents before, and I used to work in a place that offered chat help for some products, and the people handling those chats were certainly not highly trained and almost definitely gave out wrong information at times. In any case, the AT&T agent said that anyone texting from the US or Belgium would be charged international texting rates. That pretty much renders the texting aspect of this plan useless to me. Could this possibly be true? Could friends back home, unaware that I'm out of the country, send me texts only to be slapped with huge fees? Would Belgians I text be unable to text back? The main reason I'm getting the plan is so that I can text with locals while I'm there for making plans on the fly, meeting up, etc. But if those people can't text me back, that's pretty useless.

I don't really care about receiving contact from the US while I'm there. I suppose I can turn off cell data and just receive iMessages when I'm around WiFi. But I will probably need some cell data for maps and looking things up while I'm out and about. So should I just get a burner phone from a local shop for texting with locals?