Hi Jenn, I bring both Canna and Calla in after first frost. Calla first. I generally allow both to go dormant.
Calla I store in boxes in the basement. Dry with air circulation space (or in perlite or vermiculite). Dry and cool. Lift, cut foliage (see below), trim roots if you wish, allow to dry then store. If potted you can store the whole pot, cool and dry, until planting time.
Canna I've stored in slightly damp peat. Also slightly damp potting soil. Some I stored dry didn't make it.
One thing, when removing foliage from Calla cut a minimum of 2" up from tuber so as not to damage "crown".
