How do I make my motel tv to change to channel 3 or 4?

Ok so I'm stayin at a motel 6 in Corpus Christi, Tx. The tv has no A/V inputs but I have an RF Modulator to get around that. The only problem is that the tv wont turn to Channel 3 or 4 or any kind of inputs. I have an xbox I wanna play on and the channels get a little scrambled when I turned it on. I also bought a universal remote to try to get around it but it still wont change to channels not already programmed in. It says "Channels Not Available". So im thinking that its somethin with the tv. Can anybody help??? This motel has me stumped!!! I've been able to get around all the other ones but I need some geeky help quick! My tv for now is a Magnavox tv. The model number is EM6019 C121