We booked a flight to Orlando August 5-12, 2017. There were five of us flying, two adults, two minors and a senior citizen. The flight to Orlando was great, no problems. However, towards the end of our vacation, while at Hollywood Studios,I started getting text messages from United stating that they had to make a plane swap and our seating arrangement was changed. The first two times they changed our seating assignment we were still seated together, the third time they change our seating assignment we were scattered throughout the cabin. I called the airline and was told there was nothing they could do and I needed to talk to the ticket agent at the airport. I decided to try calling United again and was told the same think but if I wanted to upgrade to Economy Plus I could pay the difference. I found it ridiculous that due to their fault I would need to pay extra to be seated together. I asked to talk to a supervisor and after being on hold for several minutes I was told I would be upgraded at no cost. I think it's bad business to make the paying customer do all the work while on vacation to correct something that is out of my control and I didn't give permission for. By the way, this is the second time they have done this to us. The same thing happened last year.