The leading zero issues may arise when you want to add an international phone number.
To solve this −
<input type="tel" pattern="[0-9]*">
On iOS, the numeric keyboard appears with only numbers.
On Android phones, the "tel" is rightly interpreted but not the pattern.
You can also use −
<input type="text" pattern="[0-9]*" ...
The above will call and display the numeric keypad on iPhone and Android devices.