It may be programmed with an offset if you are on a repeater channel. When you hit the P.T.T. button do the first three numbers of your frequency increase by 5Mz? for example:
462.700 MHz to 467.700MHz ? Some radios will show this on the display. Not all. If that's the case you will have to go into your radio's settings and check. Read the manual.
When you are keying a repeater in this case, you're actually transmitting on 467.700 MHz which is the input of the repeater that then re-transmits your message on 462.700 MHz. With no offset, you would probably be transmitting simplex, Meaning radio to radio with no repeater involved. Hope this helps.