There are three ways a Traveler can request changes in his/her booking:
By using the Traveler App
By contacting his/her driver (The driver can follow the process described here and implement any changes the traveler has asked)
By contacting Welcome Pickups
Traveler Change Request Policy
Changes to the details of an upcoming transfer can be requested at any time up to 2 hours before the pickup time, depending on time zone, time of day and whether Welcome's Customer Support is live.
It is advised that Drivers keep an eye out for changes in their upcoming transfers. If the Driver can no longer accommodate an updated transfer (i.e. due to car-type capacity, schedule conflict, etc.) he should follow the process of looking for a replacement driver before removing the transfer (found here).
Depending on the changes requested the transfer price might also change. On that occasion, the new transfer price will be communicated to the Traveler, and the new transfer details will be updated once there is payment confirmation.