iPlum is a business app. iPlum number is a mobile virtual number attached to the iPlum app. You can logout from one device & login into another device with same iPlum number. The number is not locked to a device.
You can send and receive text messages and short codes using iPlum, but some apps like WhatsApp check for a number attached to the physical device. You would need to give them your physical device number to activate. iPlum may not work there.