Update travel.md for Rufbus until Sunday

docs/travel.md

@@ -29,12 +29,14 @@ If you plan to come to camp by train from far away, the website [Seat61.com](htt
     * The train from Berlin Hauptbahnhof (main station) to Stralsund or Rostock (RE5) departs every hour.
 * [live arrive/departure ticker](https://fahrinfo.vbb.de/bin/stboard.exe/dn?L=vs_newcms&input=900203709&boardType=dep&maxJourneys=50&dateBegin=15.08.23&dateEnd=20.08.23&selectDate=today&productsFilter=111111101&start=yes&dirInput=&)
 * We will provide a bus shuttle from Gransee on. See [Bus](#via-bus) below.
+* _If you arrive **before Monday, August 14th:** Call OVG-Leitstelle at least 90 minutes before your arrival in Gransee, so they can schedule an appropriate bus size: +49 3306/2307. The earlier, the better. This is mandatory, because before Monday, the bus service is on-demand._
 
 #### Zehdenick (Mark) (shuttle service to camp from this station, see “By bus” below)
 
 * Distance to the camp: ~ 7,5km
     * The regional train 12 (RB12) from Berlin-Lichtenberg to Templin City departs every hour.
 * [live arrive/departure ticker](https://fahrinfo.vbb.de/bin/stboard.exe/dn?L=vs_newcms&input=900203853&boardType=dep&maxJourneys=50&dateBegin=15.08.23&dateEnd=20.08.23&selectDate=today&productsFilter=111111101&start=yes&dirInput=&)
+* _If you arrive **before Monday, August 14th:** Call OVG-Leitstelle at least 90 minutes before your arrival in Zehdenick, so they can schedule an appropriate bus size: +49 3306/2307. The earlier, the better. This is mandatory, because before Monday, the bus service is on-demand._
 
 
 ### Special Fares by Deutsche Bahn
@@ -57,7 +59,7 @@ The [Deutschlandticket](https://www.bahn.de/angebot/regio/deutschland-ticket) co
 ## via bus
 
 
-There will be a bus service between Gransee, Zehdenick and the campground on a hourly basis.
+There will be a bus service between Gransee, Zehdenick and the campground on a hourly basis starting on Monday, August 14th. * _If you arrive **before Monday, August 14th:** Call OVG-Leitstelle at least 90 minutes before your arrival at the respective station, so they can schedule an appropriate bus size: +49 3306/2307. The earlier, the better. This is mandatory, because before Monday, the bus service is on-demand and might not be able to serve unannounced travellers._
 
 The bus will run as OVG bus line 854 with a different route and extra journeys. It will usually __either__ go to Gransee __or__ to Zehdenick, not both at the same time.