The U.S. banking system is requiring all debit and credit cards be issued with what is known as an EMV chip (Europay MasterCard Visa). Your UnitedOne debit and credit cards now have EMV chips adding to their safety. Often, when traveling out of the U.S., you will see "chip" or "PIN-enabled" on a point of sale terminal or ATM. These designations are in reference to EMV chips and their ability to authenticate Visa and MasterCard transactions.
If you encounter any signature-based transaction difficulties with a European merchant, simply complete your transactions with a "PIN-preferred" terminal. For assistance, you also have the option of contacting UnitedOne directly at 920-684-0361 or 920-451-8222 and selecting option 6.