All you need to do is un-pair the device in the settings tab of your Monimoto app and set it to the default mode.
Setting the device to default:
MM1, MM2 - by connecting it to a computer (or just a charger) with batteries inserted for at least 13 seconds.
MM5, MM6 - press and hold the button next to the SIM card with batteries inserted for at least 3 seconds.
Now Monimoto is ready for a new pair.