20% off SensatioNail Promotion

On Saturday 18th July I booked to get a pedicure done with paint and gelish done on my hands. After my treatments were completed I paid and left the store but on checking my slip I saw that I had not been given the 20% off promotional discount. I went back to the store and was refunded for the gelish but not for the pedicure. I find this highly misleading as on the website it clearly states that it applies to ALL Manis and Pedis. I cannot find anything on the website or in store that says that it does not apply to paint treatments. I cant help but feel a bit ********** and I doubt I will be back at Sorbet in future.