I've been researching the subject, but have not yet seen any definitive solution to the problem. Well, my application does send SMS from SmsManager however, it does not ask which chip to use when running in a Dual Sim application, simply because I have no idea how to do it.
As far as I know, the second parameter of smsManager.sendTextMessage which is currently declared as null is responsible for the Service Center (SMSC) that will be used for sending, which would result in sending the correct chip, in parts since the user can have a cell phone with two chips from the same operator, thus using the same SMSC for both chips.
I have checked the SmsManager documentation but there is not even any usage information on Dual Sim devices.
And here's my question: how to actually use SmsManager on Dual Sim devices correctly, always asking which chip to use, or setting it in advance?