I always called the day before. I am not sure if some of them them really accept reservations (there are some municipal and parochial albergues) but I believe it is customary. Besides, I confess that as I was walking alone in a quite lonely road, I wanted to let a kind of clue about my daily whereabouts...just in case.
My albergues:
Betharram, at the monastery (the entry is not obvious, it is a
narrow passage just facing the old stone bridge).
Arudy (one of my best experiences in my Caminos),
parochial presbytery, last rond point before the church.
Oloron Sainte Marie: Relais du Bastet (attention, many guides don't have the phone or the persons in charge right, it is currently managed by an association);
try this. It is a city, there are many options and services. Leaving the city is a bit complicated, and there is also other (and most favored) route going to Somport; in the "Relais" the hospitaleros give you a map. If you are not sure, ask for the cathedral, and then follow the signposts.
Hôpital Saint Blaise, public. It is a tiny village.
Mauleon, municipal. Ask in the Tourism bureau or the city hall, main square. It is a city; also some hostals and hotels.
Saint Just Ibarre, I stayed at a farm-albergue 1 km before the village; it does not appear in guides and the stamp in my credencial is rather blurry. I will try to get it and post here. Also, other albergues in the village proper.
Saint Jean Pied de Port. Lots of options., as you know. I stayed in the parochial, the "Accueil Kaserna"
There are many list of albergues, all in French. For example,
this one, with a lot of useful info.
Buen camino! Bon chemin!