Bad attitude from teller and assistant manager

I went collect my order at the Sunny park Sportscene shop today. I waited in line and when I indicated that I was collecting, the lady said I must look for one of the floor staff right at the back and tell them what I want (rude and poor customer service). When my parcels (a box and a plastic bag) were retrieved and everything was processed I asked for a plastic bag and they told me it was not allowed as I had bought clothes online (the teller and the lady that later introduced herself as an assistant manager backed each other up and said it is standard policy). I took my parcels and left. While paying for my parking ticket I felt undermined and inconvenienced since I could not attend to other things in the mall because it was so awkward to walk around with a box and plastic bag: I called the online shopping customer line and enquired whether that was standard policy that if you buy online you cannot be given a plastic bag.

The lady I spoke to said that it was not true that I cannot ask for a plastic bag and asked me if it was possible for me to go back to the store as she wanted to speak to the person that assisted. When I got to the store I gave the said teller the phone she called the other lady and they were busy giggling about the matter and almost instantly the story changed and said they only had small plastic bags. Then the online assistant asked to speak to the manager, the teller indicated that only the assistant manager was available. The said assistant manager while still giggling went on to lie and said they were only left with 1 pack of plastic bags and said she did not deem it necessary to give me a plastic bag as my package was a small plastic bag (never mind that I had received 2 parcels a box and plastic). The said assistant manager dragged the conversation by insisting that they were trained not to give plastic bags for online shoppers, while the teller was still giggling. I was given the phone back to which no apology was offered by the store still (I got an apology from one staff member who was completely innocent from all the drama while the two ladies continued laughing about the issue) I am disgusted by the level of disrespect in that store and to think most of my parcels are received from that store as it is on my way home from work.