Yes, you can! You can set up a default Caller ID for each user in your dashboard at Dashboard > Voice > Users .
However, you can also elect to present a different Caller ID for each call you make by creating a short code. This is a code that you type into your phone before dialling the number you wish to reach. So for example, if you had a short code of *22 to present the number you would dial *22 and then your number - e.g. *22020 8050 5141
To configure these shortcodes, simply visit Dashboard > Voice > Config > Short Codes and set up as many as you would like.
Note that some hardware "reserves" certain shortcodes for use on their specific hardware, so if your chosen shortcode doesn't work the first time, just pick another short code number or log in to the management interface of your phone and in most cases, you can disable what is often referred to as "Local Call Features". You can view more about this on Grandstream devices here.
If you need any further help today, please don't hesitate to contact our friendly support team on 020 8050 5141 or by email!