JQ01 - departing Melbourne Sunday 5/05/2019 at 3.45 pm. Direct flight to Honolulu arriving Sunday 5/05/2019 6.15 am. JQ02 - departing Honolulu Friday 10/05/2019 8.00 am. Direct flight to Melbourne arriving Saturday 11/05/2019 2.55 pm. We booked return flights with Jetstar through our Flightcenter store in Lilydale Melbourne in early December 2018. At the time we were asked if we were happy to go through Jetstar. We had never used Jetstar because we like using Virgin Airlines, but agreed to give Jetstar a go. The flights were to be direct flights - both ways, seated together and with a window. At the time we booked, we were also allowed to choose where we wanted to sit on the plane using the computer's visual of the aircraft. Happy with the booking we paid. The Wednesday before we were due to fly out, we received an SMS stating that our flight to Honolulu had been cancelled but that we had been "Upgraded" to another flight going out from Sydney. We then had to find time to go back to our travel agent for the new flight information and connecting flight information. The connecting flight now JQ506 to Sydney departing 9.10 am on 5/05/2019. Seats 4E + 4F. The new flight to Honolulu was QF6403 departing 4.25 pm direct flight to Honolulu arriving at 5.40 am the next morning. No seats as yet. This new flight time was our second inconvenience as we then had to bring our plans forward by 7 hours, make amended arrangements for our pets, and stay the night before closer to the airport. Originally, we had deliberately opted for the later flight so we would not have to do all this unnecessary fuss about but now it became necessary-sigh. Our connecting flight was OK - no complaints. On arrival in Sydney, is when the inconvenience became the nightmare. We suddenly were made aware how inconvenient we were to Jetstar. The staff seemed visibly aggrieved to find an entire plane from Melbourne had arrived needing assistance to get to their connecting flight. No one wanted to divulge any level of help. One passenger managed to find out where we needed to be to get to our tickets, so like lost and forgotten sheep in a distant city were herded together and waited for our slaughter We waited for three hours being totally ignored and I was scared as this is not my home town. They could see us, they just ignored us. We did all stay pleasant to be fair. The female desk attendant who served us was quite abrupt to us. Noticeably stressed from the facing situation, but we didn't cause this or do anything wrong. After which we still had a further two and a half hour wait before getting on the plane. We were allocated 74 G & 74 F the worst seats on the plane.When a flight attendant came around to ask if we needed anything and I asked for water, his reply - "as you are only drinking water, I will give you this one but in future you can use the tap at the back". What did I do wrong? Feeling claustrophobic, hot, woozy, - not sleeping - locked joints, aching backs, cramps, unable to move in and out of our seats effectively, we silently suffered on through the night not feeling very valued at all. Oh yes and the reclining of the seats in front made for an even more squishy experience I never want to relive. Cattle Class to the slaughter would be a more viable terminology than valued customer. Before we all alighted, the flight attendant came over the intercom with his spiel thanking us for travelling with Jetstar and how we were valued customers and that they look forward to us travelling with them again. I was so angry. Now we move onto our return flight. JQ02 - departing Honolulu Friday 10/05/2019 at 8.00 am direct flight to Melbourne. Remember… we booked and paid early December 2018… we requested to be together with a window…and selected these seats as well. We selected our seats using Flightcenter's visual seating….Now we were given our new seat numbers. 45G & 46G not even together. I am sick of excuses from Jetstar - because that is all that they are - excuses - it makes Jetstar advertisements even less credible. The two people sitting next to me were not happy with their seats either because they had selected other ones - but they said "What can you do? It's Jetstar". They also let me know that they booked tickets a long time after us - but hey they still got to sit next to each other at least- and with a window. In closing, our experience with Jetstar has not been a pleasant or positive one. Jetstar inconvenienced an entire plane of passengers from Melbourne - if the plane ever really existed. This should never have been allowed to have happened. But I feel we need some sort of compensation as this was horrific to live through.