Buses in Calais are free. Timetables and routes are on sitac-calais-opale-bus.fr.
For charging a phone, the busiest point is boulevard des Justes, at the “English toilets”. There is a session almost every day: Monday, 10:30 to 13:00; Tuesday, 10:00 to 12:00 and 14:00 to 17:00; Wednesday, 10:45 to 12:45 and 14:30 to 16:30; Thursday, 10:30 to 17:00; Friday, 10:30 to 13:00; and Saturday, 14:00 to 17:00. In the town centre, Quai de la Meuse on Saturday, 11:00 to 13:00, and Quai de la Moselle on Sunday, 14:00 to 17:00.
For water, Calais Food Collective puts containers on the living sites: Pegasus, BMX, Jean Bouin–Fontinettes, the town centre, boulevard des Justes, H2 and H3. If a container is empty, call +33 6 05 88 38 19.
A letter, a summons, a decision: with no address, none of it arrives. You can get a postal address at the Maison d'entraide et de ressources (MER), 3 rue de Croy, on Tuesday and Thursday, 14:30 to 16:00. The same place helps with writing letters at the same times.
The Secours Catholique day centre is open Monday, Wednesday and Friday, 13:30 to 17:00. On the address, the documents disagree — 39 or 47 rue de Moscou — but it is the same place; rue de Moscou is what to ask for.
The latest edition of the Calais guide is online at lc.cx/calais, and the Grande-Synthe one at lc.cx/grande-synthe. Those two documents are what get updated, not the copy in your pocket.