Samsung SCH-A645BKAATL - Manual (Page 208)

208
Section 14
• Use only the supplied or an approved replacement antenna.
Unauthorized antennas or modified accessories may damage
the phone and violate regulations governing radio devices.
• If the phone, battery, charger or any accessory is not working
properly, take it to your nearest qualified service facility. The
personnel there will assist you, and if necessary, arrange for
service.