I have been trying for the last 3 and 1/2 hours also. The change my plan option just spins and then tells me to contact in person. I have a request in on twitter and also facebook messenger, nothing is working tonight. I sure hope that I will hear from you folks that it goes through.
Welcome to the community!
Were you able to change to the $60 plan? If you were able to switch to the $60 5gb then you are good, the other 5gb will automatically be added by Fido, it can take up to 2-3 billing cycles for it to be added but it will be added.