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Buy a new remote control
There is an extremely small possibility that the remote control itself changes the TV channels, due to a hardware defect. If you are sure that the remote control itself is the reason for this issue and you tried everything else to fix it, including disassembling the remote control and cleaning its buttons, but unsuccessfully, buy a new remote control.
Note: Write down your TV's model number and take it with you when you go to a store to buy a new one.