Hi Deanna,
I'm hoping someone who's experienced your exact circumstance chimes in. One question. Was your Calla exposed to temperatures in the 30's?
I typically plant my Calla tubers in mid May, in ground and pots, and lift in Autumn just before or after first frost. Storing dry is very easy so I don't consider these annuals by any means.
I've never purchased a potted Calla, in bloom or not, so an early dormancy isn't something I've experienced. My GUESS is by keeping yours indoors until your outdoor soil temp is in the 70's and after last frost you can get it to break dormancy. I'd keep it on the dry side until you've got new growth. Then normal Calla treatment. Lots of water, regular feeding and part sun if potted (or daily watering in full sun). If in ground, full sun with a good cover of mulch to keep the roots cool and wet. Are the leaves sword shaped, lanceolate?

Dormancy would be odd at this point. If it was subjected to temps in the 40s or lower that could possibly cause dormancy but not likely. These plants ancestors originated from South Africa and dormancy is initiated by an end to seasonal rains. To much water cold temperatures and not enough light would cause yellowing foliage. Please let us know on these factors to better help you.

Scott