Networking going from 4g to 2g

I just do not understand how does a network move from 4g to 2g over night. I've been using Telkom for the past 4 years and they've been nothing but exceptional to me but since the 4th of this month my network has been on 2g I can't browse the internet I can't be on social media. What do I do now, do I cancel all my lines because they do not serve the purpose.