I think the best business plan includes a little of every contact method; in fact, if I could get their cell number I would even include a few texts.  

What does the number represented in that cell represent?  

In December I had to start calling and emailing every day or so, and eventually started calling the CEO of Zest (Tim Moore) on his cell to get my disbursement in time to pay my mortgage.

PM me and I'll give you my cell and help you get pointed in the right direction.

I don't use the pay services that will track cell phones, but I do use whitepages.com, radaris.com (but I think they just changed to an everything costs money thing, yp.com whitepages to find land-lines or "listed" cell phones.  

.), to set boundaries on hours when you will accept calls, consider a business phone line that is separate from personal cell and perhaps hire a helper to assist with simple, tedious tasks like posting ads and initial screening. 

If someone asks about it a few hours before I will just tell them to come and not get anything more than their name and a cell number in case I have to cancel last minute.

@Raul Pedrozo I have had tenants not respond to texts or calls only to find out their cell phone number changed or they didn't recharge it.

And they'll get a cell phone and you can text them.  

@Charlie Fitzgerald, unfortunately, i only have her cell numbers and her email address.