I went to a butcher and bought a items because they were buy two and get one free. The items were beef biltong. I bought 2 for £16 and got the 3rd one free. Normally they are £8 each. When I returned home, I ate one but after opening the another one we realised the second one and third one were mouldy.
I went to the butcher and requested a refund for the two mouldy ones. He wanted me to take another two of the shelf of the same product but I didn’t want it as I was put off by the mouldy ones and would not comfortable buying more from the same batch.
I asked for a refund or credit note. He offered a refund for one -£8, as ‘the other one was free’. I said that I only bought the 3 items for £16 and not 2 for £16 and got one free. I would never have bought them individually priced and now I am being forced to pay £8 for an item I would not have bought through their error.
He is a Ben Torah and said ok. I eventually took a few different items from the shelf for £10.56 – 2/3 of the £16 I had originally paid.
Having left the shop I feel that perhaps I should have double checked the Halacha.
I am happy to return to the shop if the halacha is that I acted wrongly in regards to chosen mishpat.
although it is always better to ask before acting, in retrospect, from what you are writing it seems that what you did is alright. This is because the storeowner gave you the right to get a refund for two thirds of your purchase.