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You can take advantage of service even if you have zero balance to call.
To send the callback request, key in the number of any Azercell subscriber (operator code and number) to 7700 or dial *770*operator code and number#YES. Subscriber will get SMS-notification about your request.
If you want your name to be viewed in request SMS, put a comma after the number, then add your name (up to 10 symbols).
You can send 3 requests within a day.