Only water softeners that operate using salt physically remove calcium and magnesium. Every other so-called water softener conditions, or purportedly conditions, the water. Their efficacy, however, is the matter of much dispute as it is impossible to scientifically test the water and because many factors influence the results.
Many people are conned into purchasing/installing inexpensive filters containing poly-phosphate thinking that they will completely remove all the hardness and prevent any buildup of mineral deposits in the plumbing system. This is patently false!
I am not against installing poly-phosphate filters. I am against lying to customers about the efficacy of said filters.
Oh, and those magnets sold by washing machine technicians? Garbage.
Sorry for the cynicism but it is downright criminal to mislead your customer!
As always, it is important to educate yourself before you go ahead with a purchase.