Your question suggests you have social anxiety.
The first and easiest to tackle is the fear of being cheated. If you buy a sweater of poor quality it is not the shopkeeper's fault. You must accept responsibility for your choices. Choose one place to shop. Someplace preferrably where you have bought items you have liked before. You cannot be cheated in a store where prices are clearly marked, and change is counted back. When you grocery shop do the same thing. Pick one supermarket, shop there regularly. Make sure it is a store where prices are clearly marked and change is counted back.
I am not diminishing your fear. It is called social anxiety and I had it in spades. I couldn't make it to my telephone pole in front of my apartment building because I had let fear of what might happen take over my life, but I learned how to overcome it. The way is baby steps. That's right. One small step at a time.
Repetition (the same store, the same time of day, the same clerk) will help alleviate the fear of being cheated. By picking the store as I suggested you are not putting yourself in a situation where you can be cheated so your fear becomes an internal object not an external object. You are not really being cheated. You fear you could be. Admission is step one.
As you repeat your shopping in the same place around the same time, hopefully with the same clerks try step 2. Say to yourself this is okay. I'm in a safe place. Call it a safe place even if you don't feel safe. Just that one grocery store and that one other store you choose. Or just do the grocery store first. Fake it until you make it. Then your home and that store will be safe. Shopping there will be safe.
Step 3, go to that same store and today you will smile at that same clerk you see everytime you go there. Repeat. This may be quite some time. You must reach the feel safe stage first.
Step 4, smile and say hi. Repeat.
Step 5, smile and say hi how are you. Repeat.
Step 6, smile and say anything else. Repeat.
You are building your self confidence through these baby steps and second each time you succeed in a step you are reaching out and learning to interact with more people.
At school try some of the same things. Tell yourself you are safe in your classes. Hard in Hotel Management because they are throwing you in scenarios like real work but great. You have not locked yourself away in your house yet so don't let it get there. Try to pick one person in each class and try to talk with them. If you don't click try someone else. Simple stuff. Did you do your homework? What did you get for question 10? How did you like that assignment? You decide. It doesn't have to be personal stuff but you're interacting.
Finally, don't lose hope. You will succeed. Keep telling yourself that. Tell yourself that you are good at interacting with people. Reply to any questions. Try to start up a conversation (not personal) and fake it until you make it.
Pick up a little book of positive affirmations if you need help. Tape one to your mirror while you are getting ready for school or brushing your teeth the post it on the mirror will have a good message for the week.
I went to therapy with a psychotherapist who didn't believe in all this "it's your mother's fault stuff". He actually said it was more important to talk about day to day stuff and how to improve between each meeting. I'd tell him what I had a hard time doing and he'd give me the baby step to work on. Week after week it go easier.
I work with people everyday now. Getting those first words out are not always easy and I still use post its but you know what I'm doing great. I get more self confidence every day even now, when I talk to people. I'm great at my job I love it and I actually like working with so many different people now and they seem to like me.
People are saying I've changed so much and maybe I have but the real truth is I will always have to monitor myself to be sure that I am not falling back into my old patterns of telling myself that I "can't do this" or "this may happen". This is for life for me. Even though I have confidence now the price is vigilance so I don't backslide.