Telephone SIM cards

I recommend esimdb.com as an independent site where you can evaluate a variety of options. Or check out airalo.com and getnomad.app for their offerings, which usually are well-priced and reliable.

Check out the Technology Tips subforum, there are lots of topics in there about
coverage in various countries.

SIM cards can be for a country, region, etc., and for voice and/or data, and for varying
lengths of time. There are also eSims, which do not require a physical card, but not
all phones support them.

Comviq appears to be a Swedish company, so unless you know the parameters of the
card(s) you purchased, it's likely they won't work in Greece. But you can go, try it, and
if it doesn't work, just buy new SIM/Sim cards in Greece.

I’d recommend getting an eSIM, first of all, not a physical SIM card and also id use Airalo for the eSIM. Earlier this month when we were in Greece and Italy I purchased a 30 day/20gb eSIM. In 18 days, both in Italy and in the Dodecanese on Rhodes and Symi, I’ve used a total of 5 gb out of that 20 which is amazing considering how often I was on data. It used the Orange network from France, weirdly enough, not that it bothered me. Last year, when I used another company, Ubigi, I bought a 10gb 15 day eSIM and used practically all of it and my connections weren’t as good as the Airalo connection. Occasionally, on beaches in Rhodes and Symi, my phone would connect to the Turkish network, since Turkey is close to both places. eSIM is the way to go