The BBC Trust ruled that the weekly programme misled listeners, as it asked them to submit dedications despite it being pre-recorded.
Listeners were told that they could contact the show "any time", but it was not obvious that the messages would only be played on subsequent episodes.
However, the findings stated that the BBC did not knowingly mislead its listeners.
The show is recorded on a Friday for broadcast on the following Sunday, with the playlist and script compiled on a Thursday.
A listener had complained to the BBC saying some listeners may be wasting time and money assuming that the show was live.
Radio 2 later amended the wording in the programme and phone messages to make it clear that not all messages will be used, but the BBC Trust said that they needed to change it further to make the cut-off point clear.
The BBC Trust stated that the problem was due to "essentially one of a lack of clarity" and the result of a "looseness of language".
The committee added that the programme did not "treat those who engaged with the programme fairly" as listeners could have been encouraged to contact what they thought was a live recording.
A Radio 2 spokeswoman said: "In light of the Trust's findings on clarity for people leaving dedications for the programme, we have revised the wording in order to ensure the process is absolutely clear for listeners."
Steve Wright told his Radio 2 daily afternoon listeners yesterday (January 16) that all dedications must be submitted by noon on Thursday to be possible for inclusion on the Sunday.