After a month of working out three days a week, I had gained an inch on every part of my body where I wanted to lose. The manager told me I should have done weight training. You want to fix your body for the rest of your life, and that takes time. You have to decide you want to look good next year and even better the year after that - then you're on your way. In a way, both trainers who advised you are right.
Aerobic exercise is the fastest way to burn calories.
But weight training adds muscle, and muscle burns more calories than fat tissue. I don't know why you gained an inch doing aerobics, except that it always comes down to calories in vs. calories out. It can take a lot of experimenting to find what diet and exercise program works best for you. It's taken me years to find out what keeps my body in shape. Sometimes when I want to get in shape for a boxing match and need all my punches to come out even and smooth, I have to give up the idea of toning, because if I tone too much my punches won't come out swiftly.