My personal phone is also my business phone which means a potential customer could be calling me from anywhere. My project is software that is in open beta, so

My personal phone is also my business phone which means a potential customer could be calling me from anywhere. My project is software that is in open beta, so the calls could originate from anywhere in the world. If I simply ignore any calls that are not in my contact list, I risk alienating a customer. Some might leave a voicemail, but I certainly can't count on it.