Everything you want can be had for FREE with Google Voice
When you sign up for Google Voice, do NOT select "Google Voice Number" option. Select the option that allows you to use your existing number. Once you got that done, go to your voice/call settings and set up a forwarding phone number.
I have 3 cell phone lines (1 business, 1 personal, 1 "home phone").
The number I have linked to GV is my Business line. Only a select few have access to my personal line. I have my Personal line set up as a forwarding phone on my GV, so when anyone calls my business phone and they're in my "Personal" group that I created in GV, GV will also ring my personal phone even though that person called my Business line.
I also have an office line using GV, and I use the "Do Not Disturb" feature to set up my hours of operation so if someone calls when I'm "closed", they'll just go straight to voicemail and my phone wont ring

. And the great part is that I can receive SMS or email notifications when someone leaves me a voicemail, and GV will transcribe the voicemail. Comes in handy when I don't take the call because I can still read what the voicemail says. Transcriptions aren't perfect, but enough for me to understand the message.
The great part is that you get FREE SMS messaging! I wouldn't call it a true unlimited sms messaging since there have been many occasions where I have "reached the sms limit" and had to wait 24 hours before I could send another text message. But then again, that was sending out about 150-200 text messages between several dozen different contacts in one day