You must enter a Service Name for the Phone Book Setup window entry you are adding or editing. PC Access uses this name in the list of Phone Book entries. Without a service name you would not be able to distinguish one Phone Book entry from another.
Usually you should enter the name of the service that you will use this Phone Book entry to connect to. For example, if you are creating a phone book entry to connect to the MFM Support BBS, you would probably want to use: MFM Support BBS for the Service Name.
What you enter in this field is for your own reference only. It will not affect your connection to the service.