hello. i just want to understand why this happens. so a have facebook messenger and whatsapp installed on my iphone 5s. heres the problem, i can only receive facebook calls when the app is open or running in the background, when using whatsapp i can have the app closed on the multitask and i can receive a call with no problem. i have tried enabling background app refresh and still this continuous. is this normal? why would facebook messenger have a call feature if to only works when the app is running? and why does whatsapp witch is owned by facebook doesn't have the same issue? sorry for the bad english.