Internet
In this day and age, most US cell phone networks have a customer friendly internet option. However, we are also in a world where streaming is a large part of our daily phone use. Your hotel will have a complimentary wi-fi signal for you to use.
There should be an expectation set about cell phones at Oktoberfest, though. There are close to 200,000 people located in one small area simultaneously, so it’s not a given that text messages and phone calls go through while on the grounds.