Creepy delivery guy from apollo pharmacy

It's going to be a little long since i don't want to miss out on any detail. So my sister [f20] has fallen sick and her gf ordered some medicines for her from apollo pharmacy. When the guy arrived, he couldn't find our flat so my sister went downstairs to receive the order and when she came back inside she told me what happened. She said she had to give the otp so she was asking her gf to download the app meanwhile she continued to play the game on her phone. The guy who was in his twenties and a medical college student( he himself said that so cant trust) started talking to her asking about her like what is your age, do you live alone, do you have instagram, do you have a bf and what not. My sister just answered in a yes or no avoiding eye contact. We were literally shocked because no such thing has happened before with us.Then he literally asked my sister atleast 4-5 times to be his friend and saying " sbki feelings hoti h" and "ap mujhe cute lge" and stuff and then that guy went on to talk about himself and said that he's actually not the delivery guy but his friend and that his friend was busy so he took his place. He again asked my sister to be in a friends with benefits relationship like what???? And my sister was outright denying him idk why she didnt slap tf out of him because when my sister was starting to come back and got on stairs he was still asking her to enter in a fwb. We dont know his real name and has complained about this on the app and will also complaint at the gate of our building. The actual delivery guy's name was shivam sharma. What else can we do?