The channel is not part of the set factory programmed on the decoder otherwise, if it is already programmed, it has changed transmission parameters.
So it would be best to carry out an automatic channel search on the satellite or directly on the transponder (if you already know the channel data) that transmits the channel you want, following the instructions provided in the receiver user manual.
Remember that all decoders carry out the automatic channel search based on the data memorised by the manufacturer, so if a channel is being transmitted on a new frequency, you must know all the data (i.e. satellite, frequency, polarity, symbol rate and PID) which can be found on internet or from leading specialist magazines.