yes, you can port(transfer) any phone number to any carrier. For example you could even move a landline number to a cellular carrier, and vice versa. Some carriers may charge a small fee to either move it from, or introduce it, but they cannot prevent you from porting any number.
When you sign up for the new service, simply tell them you want to “port your existing number” to them. You will have to fill out a form, provide them the carrier information of the current service, etc.
When you activate your new phone, they should have the port process programmed to kick off automatically. The carrier may tell you that it will take up to 24 hours to process, but it usually takes less than 60 minutes to complete.