If you need a change to a training date, this will require a validation/renegotiation; there are no deferrments for this request.
Also, you don't know who your Career Counselor is? It the person (with the badge), that created and processed your contract. If you cannot find your Career Counselor, send me a PM (Private Message) with your unit to include higher headquarters) and I'll find them for you.
Your Career Counselor will request a new class date from HRC; and this is called a validation/renegotiation of your contract. The validation is if they can find you a new date or if they cannot, your contract may be renegotiated so you can choose another option/MOS.