Every match that already has a reason to exist has a Suggest times button on it: a box fixture, a ladder pairing in range, a match in a draw. Pick up to six times you could play over the next few weeks, add one line if you want to, and send it. Your opponent gets a notification with your times on it, and answers in one act: tap the one that suits them, send back times of their own, or decline. A tap is the end of it, with no confirm step, because the tap is the confirm step. Times back put the same question to you, and you answer it the same way.
No contact details move, and there are none to move. Clayside holds a player's name and nothing else, so this works out of dates and a notification rather than out of an email address. Most tools in this category arrange a match by showing your opponent your phone number.
Nothing is binding. An agreed time books no court, blocks no score on another day and penalises nobody. Declining costs nothing and the notification says so. If the two of you end up playing on the Thursday instead, just put the score in: the score is what counts, and it closes the arrangement off.
Who can do it
Whoever is playing, and nobody else, including the league owner. A suggestion is one person telling another when they are free, and an organiser typing that would be putting words in somebody's mouth. It is deliberately not the same setting as Players can enter their own scores. A club that keeps the record in the committee's hands still wants its members arranging their own matches.
Changing it, and asking the whole box
Either side can Update match times afterwards, and the picker opens on the day you agreed. Calling it off is the second choice inside that dialog, because moving a match is the ordinary case and cancelling and waiting to be asked again is not.
Ask your box puts the same question to everybody you still have a match to play. The first person to tap a time gets it, and the match is then exactly like any other arranged one. It disappears from everybody else's screen, and nobody is told they missed it.
A suggestion whose dates have all gone by is simply over. It blocks nothing: either of you can suggest new times, and it never sits there jamming the match.