Best Apps to call home over wifi

If iPhones are on both ends, I've not seen anything better than FaceTime.

By the way, imo isn't blocked as of yet.

Skype...Fb messenger is also good...

I use Facebook Messenger a lot to and it is good, may be you should check the strength of you network signal. You should also try Line and [b]Tango, i use them quite often too. I don't like imo and viber i found both very annoying.
Good Luck

If you dont want to be annoyed and willing to pay a cheap rate calling home at say SR0.20 per minute then go for Zain Wifi calling.

You just need to send a zain sim back to your home country, insert that sim into an iphone and connect it to any wifi.

try namgo

Try for soma.
It's good for video as well audio calling.

IMO works like a charm for me. 

recently been using FB messenger, it just needs a VPN and u r good to go: good call quality, doesn't breakdown much and extended hours of use doesn't strain ur battery a lot