Discovery Vitality accusing client of being dishonest

In April 2019 I purchased an item off the vitality cashback promotion from Total Sports. I have followed up with them for the last year awaiting the cashback which was due to me but I have been unsuccessful. At first I was told that there is an error with Total sports and their online system. I then contacted Total sports and the issue was resolved which I forwarded to Vitality but they insisted that they needed to review and take it further. Each month I continued to follow up as I believed that Vitality has advertised so many perks I should be allowed to enjoy at least one of it, which hasn't been the case. Today, the 29th April 2020 I received an email from Vitality stating that the item purchased was returned to the store and therefore no cashback was due to me and I needed to contact Total sports for further information. I was disgusted at the accusation of being dishonest and not closing the matter correctly.