Business Phone Lines-VOIP?

I have a technical question about our business phone lines. We are a business that currently has 4 lines with Verizon and do VOIP in-house through our server. We have 1 main office number and different extensions that branch off that main number. We also have voicemail through a server and do everything through VOIP in house. We are now moving and are going with Comcast to get the phone lines needed. We put in an order for 2 phone lines with voicemail and we no longer want to run the VOIP solution in-house through our server. What are our options to continue to be able to run this successfully? We basically want to be able to have people call our main number and press 0 to speak to a receptionist, leave a voicemail if the receptionist doesn't answer, and dial an extension to get to someone in particular, or leave them a direct voicemail if they don't answer. I don't know if i need more than 2 lines with Comcast and I have no idea how to get this to work.