I wonder why networks like Airtel are not flogging twin SIM Phones. Safaricom are not their competitors. Different lanes. They will not win against Queen bee. They can however cannibalize their voice and text market. Twin Sims are the only way to do this in my opinion. Let users keep the Safaricom Line but offer them a "Mpango wa Kando" line that they can use for Data, Voice ETC when they are feeling broke. Same phone 2 SIMS.
Attacking Safaricom will only wound them. I for instance will not dump my Safaricom Line even if calls are free on the other networks. I however operate an Orange line for voice and data. Split the revenue. But Alas walk into an Airtel shop and their handsets are ridiculously priced symbian things.