We are glad to inform you that we have developed a new service...'ZeroBalance'.
It will allow you to request a callback from any other user by simply making an outbound call.
Even with 0 balance user A can dial user B, who will receive an inbound call and will be able to call back.
This service will be automatically activated starting from 21st March 2016 on all bglosim cards. There is no need to install or dial anything additionally. It is absolutely free of charge.
Please note that ZeroBalance is not available in countries with extra rates for now.
User A should be in the country with free incoming calls, otherwise he should have some balance for at least 1 minute of incoming call.