There are two types of exit rows
Row 9 is an exit row but no recline so it is available to coach travelers. However only the airport can assign them so the call center cannot help you. It does not cost extra to sit in row 9.
Row 10 has recline and is sold as MCS
Upgrades to MCS are available at 24 hours prior to departure. Price does vary based on length.
Long Haul Flights (such as New York to San Francisco) – $110
Medium Haul Flights (such as Los Angeles to Seattle) – $55
Short Haul Flights (such as San Francisco to Las Vegas) – $35