Short answer is yes
However, MobilityPass is usually providing the eSIM plan together with its own UK or US phone number. This way, when you have existing number with your plastic SIM, when you add eSIM plan, you also add additional number. So you can keep using both on one device and select which plan to use when making outbound call, as well as incoming calls for both numbers will come in.
However if you like eSIM plan to use your existing number - it is not possible. Your existing number is provided by your network carrier and we cannot assign it to our eSIM plan.
It is possible though with MobilityPass to set up your existing number as Caller ID (Alias) for outbound calls from eSIM plan (recepient will see the number you set in the settings) however when they call back, the call will be routed to the number and the sim assigned to that number.
When you assign your home or current number as caller ID (Alias) you can as well divert your current number to the ESim for incoming calls... This way your home/current number work like its your esim but billing still made by your home carrier for incoming calls..