You can add a zero before a number in Google Sheets and Excel using this tutorial. You need to change cell formatting or use function.

When you type a seven-or-ten-digit phone number into an Excel cell that uses the phone number format, Excel will automatically change the way the number looks so that it appears as a phone number.

Adding a text to a cell in Excel using Formula requires use of ampersand operator, CONCAT function, or the LEFT, RIGHT, and LEN functions.