Flight Attendant reported a total loss of electrical power to the galleys and lavatories to the Captain; who elected to perform an air turn back and precautionary landing.

Narrative

About 30 minutes into the flight in ZZZ we began to do service when we discovered that the power was out in ALL 4 galleys. The A FA (Flight Attendant) called the Captain to notify her and she told the A FA there were no indications or alarms showing that. She said she was going to call ZZZ1 and to stand by. While we waited we also discovered that the power/lights were also out in ALL 3 LAVs. About 30-40 minutes later the pilots discovered that there was no procedure for it in their trouble-shooting manual. After speaking to Dispatch; ZZZ1 Maintenance and the company Chief Pilot decided to turn us back to ZZZ because it was clearly an 'unknown' electrical problem. Once we got back to ZZZ; the Captain [requested priority handling] because we were 15;000 lbs. overweight. They didn't want us to circle to lighten up and land immediately because of the unknown electrical problem and were concerned about what else might fail. Name asked if we should do our [briefing] and the Captain said she didn't think we had to and that firetrucks would be meeting the aircraft. The Captain made an announcement letting the passengers know we would be going back to ZZZ and that we'd have another plane waiting for us. We were a total of X hours and XX minutes before we landed. When we landed there were firetrucks waiting and after 5 minutes or so the Captain made an announcement reassuring the passengers and told them it was a safety precaution having them there and that we were now headed to the gate. We had XXX passengers who were connecting to different cities in ZZZ2 so there were many people waiting and trying to rebook. The passengers were told there weren't any rooms available in ZZZ2 so many stayed in ZZZ. Our crew walked over to our new gate; got on and loaded our bags up and waited 3 hours until we had any word about what was going on. The Operations Agent got on and said; ' We're boarding now.' The A FA and I said; ' We don't have any paper work and neither does the Captain. How many people do we have?' The Operations Agent said; 'I don't know.' We asked; 'So; how are we supposed to board not knowing how many people we have or have any paper work?' The Operations Agent said; 'I don't know.' Then the Operations Agent said the system is new in ZZZ and they didn't know how to work it or tell the ramp how to load bags. We asked the Operations to talk to the Captain about all of this before she boards and then she brought back the Supervisor. The Supervisor arrived with the Operations and said she had just gotten off the phone with Dispatch and they were told they should've boarded an hour ago even if we didn't have any paper work. The Captain talked to Dispatch and explained this to them. We began boarding about 30 minutes later. We also discovered that while we were waiting that our flight---FLIGHT XXXX--- had been 'cancelled' online when we were clearly working the flight back to ZZZ2. We finally left 3 1/2 hours later after we had walked over from the first plane. Not one person from the company contacted us about this incident or asked me to do this report.The rest of the day and even after we completed the flight [Company] still showed Flight XXXX as being cancelled. Even after we actually operated and completed the flight it still showed it was cancelled. I would like to know why. Several passengers looking at their apps and trying to let family and friends know when they were leaving and arriving asked why it showed up cancelled. We didn't have any answers for them. That was both embarrassing and suspect to us.