It depends on whom you ask. According to our basic Google research, many sites indicate a cell phone will not demagnetize the credit cards, while others say it will. We anticipate most users using the Grab N Go Band for running errands and/or other short-term events.
In our opinion, using the Grab N Go Band is not likely to have any demagnetizing effect. Based on my own personal use, I have experienced absolutely no demagnetizing of any kind.