Having trouble changing my icloud account info to new apple id

I changed our apple id a while ago. Our phones have not been backing up because I have been unsuccessful in changing my apple id under the icloud account information. Under icloud in settings on my iphone, it still has listed my old apple id.(I tried to get into it but the old apple id and password arent matching up) I touched on the account to try to change my apple id but it is not letting me highlight that section to be able to change it. Does anyone have any suggestions?