If you are unable to receive the security code sent to your mobile phone, you can contact customer support, who will help you regain access to your account.
If you have changed your phone number, but still have access to the phone number that you use for 2fa, you can update it yourself.
First, you’ll need to log in to your TransferWise profile. Simply go to your Personal Profile and click on Edit settings. You can enter your new phone number and once it has been verified by SMS, you’ll then be able to log in using it in future.