Returns - lying staff/manager

Last week I bought milk from PnP in Mulbarton. On the 30th Dec, when using it we noticed it was gone sour, upon inspection of the sealed 2l bottles I saw those were already gone off, the best before date on the package was the 2nd Jan. I went to the nearest store at Trade Route to return it. The supervisor Petunia, called the manager (had no name tag, from what I recall). He was trying to make excuses, saying 7 days has passed, they are not the same type of store, etc. I explained to him about the bb date and showed him the sealed bottles. He then went to call Douglasdale - the supplier, he came back saying that they could take it back but he cannot honour that because he only has 12 litres of milk and he would run at a loss if he allowed me to return this milk. He kept going on about it. Then he said I should try the other store around 7kms away, I asked him to call them and check/let them know he is sending me there. He did that and said that they were receiving stock and I should go there. When I get to that store, I went to information and explained why I was there, one of the staff members/manager approached and advised that he took the call earlier and he told him they do not carry this product.

Is this the type of service your staff provides? What type of managers do you have running your stores? I was polite and respectable throughout, why did he lie...this type of staff are a disgrace to your brand and should not be representing your company in anyway.

Please advise when can I return/exchange this