I phone 7 no service issue

Hi I have purchased an iPhone 7 in 2017 in USA.currently I live in Sri Lanka.and now I’m having an issue my phone display shows there is no service though other phones are showing the network.later I have find out there is an issue with iPhone 7.my imei is also not showing.i contacted Apple authorized service center in Sri Lanka,and they said they can’t Repiar the phone because the phone was purchased in USA and it’s out of the region.

can you guide me on this.because of the COVID-19 travel restrictions Sri Lankan air ports are closed to there is no way of sending the phone out of Sri Lanka either

thanks