LG G3 Cat.6 — LG G3 D852- Sim network not found. Phone will restart

Hi, guys I have virgin canada LG G3- D852 just over year old and since few days it keeps saying "Sim network not found. Phone will restart"
My phone then restarts, sim is found ,it works normally for 10mins and then again I get same message and phone reboots again.
Remedies I've tried so far:
1.Deleted cache
2. Factory reset done
3. Removed sim ,cleaned area and reinserted into sim area.

Phone is running on android 6.0
So far all the above steps I've tried have failed, what should I do now, this is getting really frustrating!
Please help!