This often happens with plants that are kept outside (or bought in nursery) and then brought inside for the winter. The white fly eggs and larvae become active in warm humid temps (like in your cham cage).
Buying another plant may or may not be the solution. The next one may also be infested. Nurseries have an ongoing white fly problem because of the humidity in greenhouse. I would suggest treating the plant yourself.
*You can do one of several things, but the dunking in water is the best but, no, you do not have to do this outside
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put the plant in a plastic bag and tie the handles around the stem as close to the pot as possible. *The reason is so you do not lose a lot of soil.
*Fill a dish tub/bucket with warm water and some regular liquid dish soap. You don’t need much, 1tsp/5gal is sufficient.
*Turn the plant upside down and dunk several times to make sure you get the leaves completely wet on BOTH sides and all the stem crotches. The larvae and adult moths hangout on the underside of leaves.
*Turn it upright and let the plant site for a couple hours. The soap is what is key here. It smothers the larvae and adults.
*Rinse it in the same manner (dunking upside down) and then place back in cage. Do not worry about the soap, that small amount will not hurt your cham. Monitor the plant for other hatchings and either repeat or simply make up a solution (1/4 tsp/gallon) to spray on the leaves (remember both sides).
* you can do the spray initially but if it is a real infestation you probably will not be as successful as with the dunking.
You can buy a spray made by Safer or Concern (make sure you get the right type) and follow direction for dunking and spraying, again, any residue left on leaves after final rinse will not hurt your cham.
Regardless of what you use keep a small spray bottle and when you begin seeing more give the underside of leaves a spritz.
White flies will not hurt your cham and is unlikely to stress him – think of what he would be dealing with in the wild 
Whiteflies are a pain in the butt (my rosemary plants I bring in every year for the winter almost always have an outbreak about mid-winter (I’m in NH).
Hope this helps!
lele
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