Calla lilies are technically an 'Aroid' so you would get a better answer in the ariod forum rather than asking us lily nerds here in the lily (lilium) forum. It is highlited in 'red' above. However, it sounds like your plant is going thru transplant shock (somewhat the normal thing). Also, I'd question whether the office fluorescent lighting is providing enough of the correct light wavelength and whether it's intense enough. Be careful not to over water at this time (just keep moist) and don't fertilize until it is actively growing again. But again, ask those people over there in the Aroids forum. Lots of Calla lily experts over there.