Hon, immediately call your GP and see if they can help you with either a small prescription to get you through a few days or with a new prescription for a step-down drug like Tramadol. That "we'll deal with it Monday" line is inexcusable! You need to be sure the surgeon hears about that from you in person, not on a voicemail.
If you find yourself in pain over the weekend and all else has failed you, go to a nearby Emergency Room or walk-in clinic. In fact, you could go to a walk-in clinic today and see what can be done to get you through until Tuesday (instead of just Monday, just in case...).
I feel so bad for you. This is absolutely horrible customer service and care. I'm sorry you are having to go through with it. Please, please do not feel like any of this is your fault or you are doing something wrong. You are not!!
The only other thing I could suggest this late on a Friday is to maybe call the surgeon's office back and ask to speak with a supervisor who is above the nurse you talked to. Also, don't hesitate to call the surgeon's number again and leave a message that you are in severe pain and you need to speak with him immediately. Call until you get him.