Can I change the phone number registered to my account?

For security reasons, mobile numbers cannot currently be changed after account registration.

What to do if you changed your number and want buyers to contact you?

All you need to do is log out, create a "New Account" using your new mobile number, and post your ad from there. 

Your new number will then be visible to all buyers. (Ensure your new number has an active WhatsApp account to make communication easier).