anyone have any information about iphone 6 and 6 issues with receiving Unknown caller IDs from pbx systems?

We are seeing any issue with iphone 6 and 6+ phones receiving "Unknown" on the caller id when they receive a call from a PBX system. All other versions of iphones are not having this issue. I have read several forums and it seems to be a carrier issue with the new LTE towers. Has anyone else experienced this issue?