Recently, I have submitted a mathematical paper to a journal published by Taylor & Francis. After some days, the status of the paper was changed from Submitted to Journal to AWAITING REFEREE SELECTION. Up to now, 11 weeks passed but the status is still AWAITING REFEREE SELECTION. I have contacted to Editorial Office several but the result is not changed. How should we respond to them in this case?
There is little you can do, actually, and eleven weeks doesn't sound excessive. That is especially true if the number of potential reviewers is small, as for an esoteric paper. But kicking them more isn't going to get them to move any faster, and might make them move slower if they get upset. Adding to their workload by needing to respond to you doesn't speed them up, of course.
Some academics have a different schedule at the end of a year and the first of the new year, so that might account for the delay.
But they really have no incentive to slow it down and every incentive to make it work. If you have no trust in them, withdraw the paper and submit it elsewhere, knowing that the clock restarts if you you do that.
There is also, possibly, some time delay in changing the status even after reviewers have been found.