If you made an extra booking that has the exact same transfer details as your original booking, the Welcome Support team will send you an email notification so as to make you aware of the 2 similar bookings.

Via this email notification, you will have the option to cancel the extra booking.

For more info on this, please take a look at the following articles:
​How can I correct the errors in my booking?
​Why did I receive an email notification asking me to correct a detail of my transfer?

Alternatively, you can also cancel the extra booking yourself by following the steps in the following article:

How can I cancel my Welcome transfer?

You can also review our refund policy here and read the following related article:

When am I entitled to a payment refund?