It's hard to book an appointment with them through phone as they are all busy from the time they open the centre. I booked mine through email but it took few days before I got an answer from them. It's just 2 exchanging emails. First, emailed them about booking appointment for UK visa with the date and time u wanna have the test then got an email and just answer all the questions they asked then after that they will email your reference ID and just bring 2 valid ID's during the test!!!!!!