My Terrible First Day At Work.

So today was my first day at my first job as a direct sales representative. My short story begins a few weeks ago. My older brother hooked me up with a sales rep interview at one of the local microfinance banks in my hometown. I knew this was not a good pairing for me because I am terrible at speaking to people I have no relationship with. I am more of an introvert and not very sociable. However, I decided to do the interview anyway because I was under pressure from parents and siblings to get a job.
I was sure I flanked the interview because during the interview they asked me to do a sales pitch and my mind just went blank. I could not form complete sentences and I just had to shut the hell up since it was embarrassing. After that short episode it became even more difficult to answer the follow up questions. I remember they asked me if I have a follow up question and I asked when I would expect a response and the female interviewer laughed. I believe that’s just how bad it was.
I never got a response for over a week and a half and I knew I did not get the job and I was kind of relieved. Last Thursday my brother texts me and tells me he has spoken with the manager at that bank and says I should expect a call. On that evening I received a call from the bank and told me to present my documentations the following day. On Friday as I was presenting my documents I got to check out the offices and noticed they only had one teller and three work computers. The place was filled with employees and I had to ask myself why so few work computers with this many employees?
So today I finally got my answers. I realized there are only seven permanent employees: The bank manager, one bank teller, one customer care agent, leader of sales reps and two loan processing officers. Sales reps total a number of twelve. I joined the bank on the hopes that if I worked diligently enough I would be offered an opportunity to transfer to other departments where I am more comfortable. Now all those hopes have been dashed. I do not have the necessary qualities to be a successful sales agent.

That is not all, I spent the day with the manager and three other employees on the field, to ‘learn’ the ropes of the job and he seemed a nice enough guy. When we went back to the office, the tone changed. At the end of the day he holds a meeting where all sales agents report their day’s sales and those who had nothing to show for their efforts were seriously berated. Surprisingly most had just sold one bank product. I over think a lot and seeing that did not help at all. Now I have put myself under a lot of unnecessary pressure despite the fact that I am new and will not be subjected to that kind of treatment in the first two weeks or so. I am now afraid of what will happen when the manager decides am no longer new. I do not want to disappoint my brother because I know he got me the job. Neither do I want to disappoint my mother because she just can not wait for the day I will move out.
I need advice from someone who has been in a similar situation before. I am not a lazy person that I need whoever is reading this to understand. I interned at a similar bank only with larger departments. I worked at their credit section, customer care department and their teller section. My efforts were good enough that I was offered a job but sadly I had to return to Laikipia University, Kenya to complete my studies. At the moment they have no positions open.
Please give me helpful advice. I have heard of stories of people who end up working at jobs they do not love and they do not often end well. I do not want to end up depressed, I have too much to live for.