Hi there @six6sux and welcome to the Community!
Here are the steps to do this online from your account (You'll be given a list of numbers to choose from. If you don't like the ones displayed, you can click to load new ones):
1. Sign into your Fido My Account.
2. Select the wireless number you want to change.
3. Select Change My Number.
4. Select the Province and City for the number, then click FIND AVAILABLE NUMBERS.
5. Choose one, then click Select Number. Follow the on screen prompts to complete the phone number change process.
Visit this link for things you should know about changing your number.
Hope this helps.