hi there, is there a plugin that changes’ the beat frequency?
Are you talking about the tempo (beats-per-minute)? There is a Change Tempo effect. For small changes, you can try Change Speed, which will change the temp and pitch together and is less-likely to “damage” the sound.
If you want to change the pitch (frequency) of the bass there is a Change Pitch effect, but that will change the pitch of everything (i.e. transpose to a different key).