Response of MNOs in Middle east to VoLTE

Did VoIP (Voice over Internet Protocol) at 90s of 20th century and 1st decade of new Millennium which provided almost free internatonal calls, threat revenue of classic GSM (Global System for Mobile communication) services (calls & SMS)?

Did VoLTE (Voice over Long Term Evolution) and OTT (Over The Top) services using 4G (4th Generation), chatting and free calls become a real threat to regular business of Telecom companies?

How could MNOs (Mobile Network Operators) save the revenue of the classic GSM services competing with freec calls and chatting provided by VoLTE and OTT services?

MNOs usually are the providers of internet services used by OTT services (Facebook messenger, WhatApp, Viber..) as carrier. How MNOs use this as an advantage in competing with VoLTE?

Some MNOs at middle east blocked the most popular OTT services at their networks. Is this a valid economical solution to save revenue of classical GSM services from both effectiveness and continuity points of view? Please elaborate.

Every industry life cycle ends by decline phase. Do we live decline phase of telecommunication industry at middle east? Please elaborate.

What are the recommended change could MNOs apply to save their business in the coming period?

Please specify the country/ies in which you worked in Telecommunication industry.

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