[inquisitor]

Solomo surely have cheap roaming rates especially for outgoing calls through their callback service. However their callback service is unreliable and some phones (e.g. some Samsung phones) even don't support it at all, since it is a tweaked STK/USSD-solution which seems not to be complying fully with standards.
Further there are dozens of reports on the solomo customer forum of solomo SIMs not even registering on foreign networks.
You should know that solomo is based on a MVNO called vistream and vistream is a real MVNO running some essential core network infrastructure by their own while they basicly only use the cell towers of eplus. However vistream have a lot of problems with their infrastructure - e.g. a lot of users experience no calls and SMS coming in while there's an active data session.
This combination of the messy, overloaded eplus network plus the buggy vistream infrastructure results in an inferior product, which I just cannot recommend. You may end up spending way more money if solomo once again does not work.