Is it "free roaming" true?
 

i saw a few online store sold a type of prepaid SIM, called "travelSIM" or "PassportSIM", all of them claims that "the SIM is Free to receive Incoming Calls in over 50 countries", is it ture?

i wonder how can they do that, who knows the platform provider of such free roaming solutions?

ps. most of the primary number(or active number) is +44(Isle of Man) or +372, are these area any special terms in telecom industry?

thank you guys!

Welcome to the forum.
They make their money because the caller is paying a large premium to call them. In fact, the cost to dial a +372 SIM was/is so high that some long distance carriers (at least in the U.S.) refused to connect calls because of the irate calls from customers when they got their bill at end of month. I know dialing Mann (+44) numbers is somewhat expensive to call, but not as bad as +372.
You need to check the prices for calling these numbers from your country.

...mike

There is indeed a high price you pay when calling +372 numbers and I would advice not to use a card in this number range. some carriers (voip) don't even connect to these numbers.

If you want to buy a card get one that has a +44 number, using voip you can call these numbers for 5 to 6 eurocent / 8 dollarcent per minute.

some card providers also have a fair use rate meaning that if you receive to many calls and not make any calls you will be disconnected. so for example for every 5 incoming calls you have to make 1 outgoing call. They look at this on a monthy, or serval month time frame,

The call rates that some cahrge have setup fee and they really only make money on outgoing calls and this pays for the incoming calls.

So basically stay away from +372 number, go for a +44 number, check the smallprint and if you read fair use, stay away if you expect to receive many incoming calls and not many outgoing calls