MrClass wroteI was in the same situation; got an iPhone XS plus. Traveled to Beirut; got the message upon inserting a new sim; 6 months later, traveled again, phone still works despite being well over the 90 days period.
Only God knows what the heck is going on
The text message you get from MoT specifically says that "you have 90 days of usage
per year" thus you can potentially come for a 15-day trip up to 6 times a year and you'd still be fine.
I recently got a Xiaomi Mi 9 SE. I don't think it's officially available here so I will let the 90 period run and see what happens. Hoping that it will not be included in the customs list.