There is likewise an annoying process on iPhones when you switch SIM cards. The iPhone sends a chargeable SMS to +44 7786 205094 and/or +44 7537 4102X1. These numbers are Apple's iMessage and FaceTime activation servers hosted by Vodafone UK. Presumably this happens on the iPhone every time you change IMSI; it certainly happens with an Orange UK SIM card when switching between lines on
Enhanced Line 2. As Toggle have yet to issue nano-SIMs, I haven't been able to test this yet on my iPhone 5.