What's currently the best way for iPhone user to call out via Thirdlane?

Hey gang, having end-users with the need to dial out from their cell phones but having their company's callerID # show up and not their cell #.

While Thirdlane Connect offers a great way for android users to dial out of the PBX via WebRTC mode, what is the best way currently for an end-user to dial out from their cell phone? I remember the Dialer app used to work great for this (especially since it used the celluar network and didn't relay on spotty 4G data coverage ) but I understand it's no longer supported and I don't know if it was/is available for iPhone.

I'm trying to keep everything in house with Thirdlane and avoid having to use a 3rd party app like Zoiper. Any suggestions?