We used to tell our customers a peice of ice on the dent let it melt then dry and hover that works
also
You can use a damp cloth and and a hot iron to remove carpet dents. Place the damp cloth over dents and place iron on a few seconds and check. Keep the cloth damp.May take several minutes.
I had a huge metal framed sofa that dented the lounge med. pile carpet it is the cold not just the moisture that does the job - so I put a thin sheet of polythene a huge amount of ice ( all along the six foot grove ) on the top topped with bounty to collect water when it melted (I knotted the dust sheet to keep all water in it.) . Went out for half an hour, then lifted the lot got a couple of ice cubes and rubbed in the groves to raise the pile using a nail brush to help worked a treat!