Microsoft is shutting down its video calling app for its first generation of smartphone handsets and for some older Macs and PCs too.

One of the world's most popular VoIP services, Skype is available on iPhone, Android devices and of course desktop computers. But as competition heats up, and as consumers move away from PCs to mobile devices, Microsoft is improving the service with new features and unfortunately, as some users are this week discovering, not all devices can support the upgrades.

The hardest hit will be Windows Phone 7 smartphone owners as Microsoft is pulling the Skype app altogether, not simply dropping support. If you're a Windows Phone 7 user, then the only way to continue using Skype is to buy a new phone.

If this isn't feasible, then the best thing to do is to cancel your subscription and approach the service's customer service department to see if you qualify for a refund.

But as well as Windows Phone 7 owners, a number of Mac users have discovered over recent days that they too can no longer log into their Skype accounts or make voice or video calls.

Initially, this seemed to suggest that Microsoft was dropping support for all Mac desktops not running Mavericks — the latest edition of the Apple desktop operating system — but Microsoft has now clarified the issue.

It is dropping version 6.13 of Skype, which most Mac owners with computers running OSX 10.6-10.8 use, but it will continue to support a slightly newer version of the application — version 6.15 — that should be compatible.

This will help Mac users to keep using the service, for the time being at least. Microsoft wants to drop support for that version too and have all Skype users running the latest version (6.19) but as with Windows Phone 7 owners, that will mean upgrading to a newer Mac, capable of running Mavericks or the upcoming Yosemite version of OSX. — ©AFP/Relaxnews 2014