Changing default country code for phone number

How do I go about changing the default country code dropdown item? Right now it showing Vietnam as the default starting country.

Hi Alex,
To change the Default Dial Code, please follow these steps
1. Go to Back-end > OS Services Booking > Configuration > Tab: SMS Setting
2. Change value of dropdown select: Default dialing code
Thanks
Dam

Thank you. I changed it to Canada-1 but reverts to USA-1. Not sure why. For now I have just disabled the dropdown.

Speaking of the booking form. Is there a way to give people the option of signing up for a user account or booking without a registering?
Seems like its one or the other.

Hi Alex,
In OS Services Booking, we don't have feature to allow people to sign up without registering. User should register to become Joomla user before they can login to continue booking progress.
Thanks
Dam