Need more information.
Single-handle? Double-handle? Frozen as in ice or "frozen" as with built-up mineral deposits?
If it's mineral deposits and single-handle, you can turn off the water to it and unscrew the ball cap counter-clockwise with a pair of channel-lock pliers and soak all of the parts in vinegar to dissolve the minerals. That will free it up.
Actually, you probably need to get a Delta repair kit and replace the internal parts.
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