Yep, you can.
Requests to extend treatments is very common (it’s a great compliment to therapists by the way!) – especially for 60min massages.
If you wish to extend your massage, simply ask your therapist. If your therapist is available (e.g. he/ she doesn’t have another client to go to), he/ she will simply "Extend" the session from his/her Blys Pro app, and add the extra time to your booking (15min, 30min or 60min). The difference will automatically be charged to your account so you don't have to move a muscle.