I seem to face an annoying problem with my IPhone. I can't use data while i'm on a call. No matter where i go, it's the same. Anybody else facing the same issue? Is there a fix for this?
iPhone 6 Plus, iOS 9.3.4
This article may help.
About cellular data settings and usage on your iPhone and iPad - Apple Support
Who is your carrier?
Some carriers do not support Voice and Data at the same time.
Verizon was one of these carriers in the U.S. until 2014 with the iPhone 6 & 6Plus when they enabled their Voice over LTE support.
Can't use cellular data while on the phone
