I noticed that the new Microsoft Edge browser overrides my styles when it detects phone numbers:
(123)123-1234
The above answer works perfectly, but disables the ability to have click to call phone numbers (which is a major problem if you are building a responsive site). I have found a better work around to be make the phone number a link. Example:
(888) 888-8888
This would then allow you to style the "link" however you want, and the "a" styles in your CSS override the Edge and iPhone styles on the phone number. The only issue with this is it makes the phone number a link for all devices, but I have found this not to be an issue as almost every device has some sort of click to call feature or app included.