Channel changing to busier channels despite setting a channel manually

Hello, I'm finding daily that my 2.4ghz channel and sometimes my 5ghz channel are changing from the channel I've set it to. Whenever I use my phone to see the current channel and the traffic, it's always changed it from the channel it was set to (which is the quietest in my area) to one that is busier. The 5ghz will change channels, sometimes to another empty channel, however it has also set it to the same channel as my neighbours at times when there are plenty of empty alternatives. Could you please turn off the setting that causes it to change automatically please? Many thanks!