While the Square credit card reader system does have phone support available for users, it does not provide a phone number for use with Square's transaction system. All Square transactions are performed through Square's app software over the Internet.
Though it is not possible to use Square's transaction system over the phone, it is possible to use the Square transaction app without the physical Square reader itself. Users are able to manually key in credit card information into the app if the reader or physical credit card are not available. However, Square charges a larger transaction fee for manual transactions.