As has been said above you might well need to accept a more junior position, such as an Ops Assistant, before you can become a Controller. Thats what I did and became a controller less then a year later.
Maybe even start of in crewing as that will give a good understanding of Flight Duty Periods etc that are important to know about as an Ops controller.
Most airlines will have seperate Ops and Crewing departments, although where I worked we did both.
The number of Airlines with Ops control has decreased slightly after a number of takeovers where the airline bought out has an Ops department that becomes surplus to requirements, but there are still plenty of jobs going out there.
Some Airlines advertise Ops jobs on their websites but a lot of it is done through a well known Aviation Job Search site (Clue there if you don't know about it already!!). There are always vacancies on there. Maybe try a smaller airline / business jets first if you see nothing from the larger airlines, they are a good way to build up experience as you normally have more involved in the role, such as Ops and crewing combined into the Ops controller job.