Hello Aspirant
In most cases, this is not possible. Once you have taken admission at an institute in a particular stream, it is not possible for you to change your stream. Especially when you have paid the fee.
But in any case, you should talk to the Administrative office of your college and tell them your concern, they'll be best at solving your query. They may ask you to write a letter and get it signed by various authorities.
However, if they don't agree, you can leave the stream and take TC. After that, you may be able to take admission again at college and in the particular stream that you desire. Switching between streams will be possible that way then.
Hope this helps