The Epsom Salt
(Magnesium Sulfat Heptahydrat) you got is the right one!
Pure Magnesium Sulfat can not be dissolved in water. It has to be hydrated, to be water soluble.
The chemical name of Epsom Salt
Magnesium Sulfat Heptahydrat. (MgSO4x7H2O)
(Magnesii Sulfas Hepatahydricus)
Sometimes it is wrongly called: Magnesium Sulphate Hydrated.
EPSOMITE is the name of the same Mineral: EPSOMITE
KIESERITE (MgSO4 + H2O, Hydrated Magnesium Sulfate)
Hexahydrite (MgSO4 + 6H2O)
Heptahydrat is not some nasty chemical, it is the name for "7H2O", seven molecules (7=hepta) of pure clean WATER (hydrat = H2O).
AS this form of Magnesium Sulfat is the only form used for human and animal consumption, you will often find that the third word: Heptahydrat(Hepatahydricus) is not even written.
So, it is most likely that all Magnesium Sulfat sold in all pharmacies all over the world is actually Magnesium Sulfat Heptahydrat, but on some packages, word Heptahydrat have been omited, as it is not important to specify it.