You can discuss this with your teachers and Director of Studies who will be able to best advise you on a new course to suit your needs and level. You can then speak to the Admissions staff who can change your booking, subject to availability. Please note there may be an additional charge.
In both the UK and the US, you will need to make sure that the course you wish to change to meets your visa requirements. For example, in the US, if you are on an F-1 student visa, you will only be allowed to change to another full-time course of 18 hours or more per week.