Hi Paul:

Tasks such as internet banking, which are accomplished through a web browser on the phone or a bank-specific app, will work regardless of what kind of SIM card is in the phone. This I know from personal experience, having used Moroccan, Italian, etc. SIM cards in my Canadian iPhone when travelling through those countries.

I also know that Skype is SIM-agnostic.

As for WhatsApp, I think that particular app is tied to the phone number of the device, which means that you might have to re-register each time you change a SIM card. But, an easier work-around would be to just use Skype.

I am not familiar with Polarsteps, but from a quick look at the documentation for that application, I don't think it cares at all about your SIM card. So you should not have any problem with it.

A possible way to check ahead of time to see if everything on your phone would work with a foreign SIM card would be to simply remove the SIM card from your phone, then connect to the Wi-Fi network in your home (or local coffee shop), and test the apps to see if they work OK without a SIM card installed - in other words, via Wi-Fi alone. If they do, then that assures you that the app has no dependency on the SIM card.

For sure, though, it would be a heck of a lot simpler for you to just buy prepaid SIM cards in the various countries as you pass through them. Keep in mind that in lesser-developed countries, GSM telephony has leapfrogged way ahead of landline-based telephony. The Wi-Fi that you might find along the way in locations such as hotels, restaurants, etc. relies on landlines, which typically have poor throughput in sub-Saharan Africa. GSM, on the other hand (connecting via a SIM card in your mobile) offers a much faster and more modern connection to the internet.

Michael