Reversible competitive antagonists associate and then dissociate from the receptors:
they do not STAY associated with the receptors. Show this in the diagram below.

Their effects can therefore be reduced by adding more of the agonist: as the agonist concentration increases, there is a greater chance that a receptor will become occupied by an agonist molecule rather than an antagonist molecule when an antagonist molecule dissociates to leave a free receptor.

The effects of the antagonist can be REVERSED.