Minimum number of characters (numbers) in the phone field

Alfonso,

I have been waiting to see if someone wanted to constitute you, but seeing that nobody has written something to you, I have encouraged myself to answer.

There is a plugin for the entry of telephone numbers. Free Plugins

In addition, in a standard way you have masks and regular expressions (these are very potent and there are many examples on the Internet).

Expresión Regular

I hope I have helped you in your problem.

Cheers,
fernando