No exchange for the device they open instore

No exchange @ vodaworld I went to vodaworld on Friday 30th Dec 2022 and I end up buying honor x8 unaware that it a single sim because they do Sim exchange in store for (they actually opened that phone for us), when I get home trying to put my internet Sim to find out it's a single Sim, the next day 31st dec 2022 went back trying to exchange only to be told that they only exchange if the device is faulty