Ability to call out on multiple lines per each phone device

Our situation. We have a four office personnel who work together to answer the phone all the calls that come in.

Our company has two distinct phone numbers with two different area codes. We have two different area code numbers as clients we contact that are in a different State tend to never pick up an out-of-state number.

The ideal situation on our phone device is to be able to select the particular line to call out from that area code. When we would like to contact a client in area code "A" any of the office personnel can select line 1 on the phone. When we would like to contact a client in area code "B" we can select line 2 on the phone.

Currently, each phone device can only be assigned to one phone number and can not be shared between the group.

But I can imagine this would be helpful to any company that uses different phone numbers for whatever reason.