Businessman preventing two people from transacting a sale on his property

Q: Could mufti advise on the following: 

Person A owns a Cash n Carry, person B and person C both are his customer's and purchase from him. At the premises of person A, person B and C meet and start transacting on person A's premises. Person A in turns tells Person B that person C is my customer and you cannot supply him. 

1. Is this type of clause permissable in shariah where person A stops person B from supplying person C as he feels it's his customer. 

2. If person B and C transacted on person A's property, is the sale valid.

Overcoming one's fears

Q: Wherever I work, I am always afraid of the people and have fear for people. 

When I am given some work, I start thinking a lot about how to do it and what to do. 

The fear of the boss and some other people is sitting in my heart and mind. I don't have much mental peace and I make silly mistakes, small mistakes happen easily which become big. 

I also have fear of taking leave, fear of work not being completed, fear of asking something, I have all these fears. 

My dream is to get a job in the government or a company like that nearby. I have applied at many places but I am failing and I am not getting a call from big companies and dream that our home loan gets quickly finished. 

I request for a wazifa, Amal or Taaweez if any to benefit myself and also that my home loan gets finished up soon.