Terrible Service from Dischem Store Manager

I am unhappy with the service I have received from Dis-chem. I bought Sela teabags for a loved one not knowing that she has gastric ulcer and will not be able to drink the tea. When I tried to return the tea or rather exchange it for something else. Mr Daniel (Dischem Store Manager at Tshwane Regional Mall) refuses to assist me in the exchange stating that they aren't allowed to return such items whereas the Cashier did not inform me when I bought the item that I won't be able to return the item. I am truly disappointed in the service I've received, the manager was not helpful at all.