Apparently I can only return a product if it is faulty with mtn and no other reason

So I signed a contract with mtn for a tablet that I requested it should be able to connect to a keyboard for school work purposes. Although on the pamphlet it came out with a cover and s-pen, I made it specific that it should connect to a keyboard & the lady assisting me assured me that although mtn doesn't have the keyboard in store I should be able to get it at Samsung or other retailers like Matrix. Few days later of searching for a keyboard without any luck I returned the tablet within 7days recommended period only to be told I can only return a product if it is faulty not because it does not meet my needs. Worse part I did not want to cancel the contract but upgrade to S7 tablet which will meet my needs. Almost 2 months my issue not yet resolved yet they deducted money from my account, MTN, I totally regret walking in your store that day.