TextNow, Skype, Globfone, Viber, Hushed, CallJoy, CloudTalk.io, 2ndNumber, JMP.chat, MightyCall, Phone.com, YouMail, Ring4, Telzio, Heymarket, Starleaf, Phonebooth, TinyVoicemail, Zaplee, Respond Flow, CallingVault, Talkray, Thirdlane Connect, TENIOS Voice API, net2phone, Ringio are some alternatives to Google Voice.