You wrote,

"Some customers complain they don't read email" and then

"I don't have a lot of time to look up the phone carriers of hundreds of customers to find up their phone carriers and update their client records."

I took "some" to be a lot less than "hundreds".

In any case, you have hundreds of customers that won't read email, but they have smart phones, which have email built right in, and they won't read your mail when they get a email notification, but they will read a text when they get a text notification? If so, that's probably a rather unique case and not a problem shared by many QuickBooks users.