I want to upgrade my United Airlines economy class ticket to business class for a more comfortable flight experience. How can I change my reservation without canceling?

Economy Class and Business Class are two distinct cabin classes offered by airlines for passengers with varying preferences and budgets. Consider these options to upgrade from economy class to business class on United Airlines without canceling your reservation:
• Seat availability determines upgrades. Check for discounted business-class fares before upgrading with miles to see if it's cheaper.
• Select Upgrade-Eligible Flights: Use the advanced search tool and enable "MUA" (Mileage Upgrade Award) when booking. This helps you find miles-eligible flights.
• Upgrade Methods: United Airlines offers several seat and cabin class upgrades:
• When making your initial reservation, you can choose United Polaris® business class, United First®, or United Business®.
• Change Seat or Class: After booking, you can change seats or classes.
• Benefits and upgrades are available to MileagePlus® members. Upgrade and benefit eligibility depends on MileagePlus status.
• Regional Upgrades: Upgrade availability varies. Know that Continental U.S., Hawaii, Alaska, Canada, Mexico, the Caribbean, Central America, South America, Europe, the Middle East, Africa, Australia, New Zealand, Asia, Japan, Guam, Micronesia, and Tahiti offer upgrades.
• Make sure your ticket can be upgraded. PlusPoints upgrades are not available for Basic Economy and "first bag charge, no changes" fares.
• Contact for Help: Visit the United Airlines website or call the United Customer Contact Center in your country or region for help.
It's advisable to contact the airlines for the most up-to-date information, as companies frequently revise their policies in response to new developments.