If you are using You can book me (YCBM) you do need to pay for the subscription and buy text credits or it won't work.
A lot of people add their card on file but don't actually pay for it. You will need to be sure that a charge has been made otherwise it is NOT active.
If you still need to upgrade it, just login and look at the image below.
P.S. for MGS Clients, be sure to submit your photos and logos in this link: