Something I found out on my last trip from an expat friend in Cuba is that "somebody in Cuba" is cloning some users' phones, that is, phones with a Cuban sim card. I'm not sure about international sim cards.
In case anyone might be worried that this may sound like a groundless accusation of underhanded dealings, there is a code that lets you check and see for yourself if it has been done.
With your Cuban phone, open the phone app and dial *#06# and press "Call". the following screen will open on your phone, this has to be done in Cuba of course, on the Cubacel network. Edit. This works outside of Cuba too. I just checked.
I've blurred out some of the data. One clone is enough thank you!
This phone is dual sim so there should be one IMEI (International Mobile Station Equipment Identity) code and one MEID (Mobile Equipment identifier) code for each sim.
If this screen shows more than one code for each sim in your phone, your phone has been cloned. And somebody else can see everything you do on your phone. Calls, messages, etc. They can even make calls and send messages using your account.
I have been told that this is done to phones that show "unusual" activity. "Unusual activity" can be an odd mix of sending messages to Cubans and tourists, international and local, as I do, and lots of us do. Quite a few Cuban locals told me their phones have been cloned too. About 50%. Mostly in the tourist industry, so again an odd mix of messaging and calling locally and internationally.
I don't care personally, I have nothing to hide, I don't care if somebody sees what's on my phone screen, and I know no calls have been made other than from me.
I have been told, if you change phones, they will know and will update the clone identity from your existing number.
If you change your Cuban sim card/number, they will update the code from your existing phone ID.
So the only way to get around it is to put a new sim card into a phone you haven't used in Cuba before. Then they have to start again.
Just a heads-up!
Edit. I just did a test and it seems that *#06# isn't a Cuban thing, it seems to work on any phone, anywhere, to check your IMEI code on your phone.