The Lumia 640 is now on sale in the US, via Cricket Wireless, and Microsoft is supporting its release with four new, 15-second TV ads that show the smartphone's use as a personal assistant, via Cortana.

One clip shows how Cortana could have helped a husband remind his wife that the plumber was going to be in the house, to help avoid a surprise encounter. Another ad shows how Cortana and the Lumia 640 could have reminded the founders of a start-up company that their investors would be making a visit, so they won't be playing with their office drone at the time.

The third commercial shows how Cortana might have helped a person to not bring a glazed ham to a kid's birthday party, while the final ad shows that a TV weatherman might have arrived for his news broadcast on time if he used Cortana and the Lumia 640 to give him traffic alerts.

These clips show that Microsoft is still interested in promoting Windows Phone 8.1 and its newest Lumia devices in the US, even as the company prepares for the launch of Windows 10 Mobile sometime this fall.

Source: Microsoft Lumia (YouTube)