Narrative:

We were giving a descent clearance to FL240 by ATC. The captain then heard back from the flight attendant to go back and use the lavatory. Shortly after; chicago center cleared me direct to prise intersection for the watsn two RNAV arrival and descend to; I thought; FL220 even though we were on the veeck one arrival. At the same time the flight attendant who had entered the cockpit was asking me a question. I tried to read back the clearance but got it wrong because I was unfamiliar with the new arrival and at the same time tried to get a read back of the altitude. I don't remember clearly but I think I read back FL220. I also tried to get a heading while I figured out what the new fix and arrival was. It took a while but I got a heading while I searched for the arrival. This was happening while the captain was buzzing to reenter the cockpit. I dialed in the new heading and then talked to the captain to let him back into the cockpit. As he came in and I was passing through some altitude below FL240 center said 'I'm not sure what you're doing but descend to FL220.' I then looked up and saw 310 set in the alert window. I then redialed down to FL220. When I tried again to clarify our new RNAV arrival; center cleared us back onto our original fix and on the original arrival. I then thought about it as we made the arrival and wasn't sure if something had happened or not. Looking back I think I might have moved the altitude dial when I meant to move the heading bug. Also I am not sure about the altitude given by ATC. On the ground I let the captain know of my concerns and suggestion to write an as soon as possible.I should have not moved the altitude alerter until ATC gave me a more affirmative answer to my query about my read back. When the captain called to reenter the cockpit I should have momentarily ignored it while stopping my decent to clarify the altitude clearance. ATC should have given me a heads up of a clearance change before giving me the new clearance. It was too much information to all of a sudden be given the new arrival; the new fix; and new altitude at the same time. It should be easier to clarify clearances. I've noticed often times when I make a query it takes a while for ATC to reply back if at all.

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Original NASA ASRS Text

Title: A319 First Officer reports being assigned direct to a fix on a new arrival and a descent clearance as the Captain is leaving the cockpit for a lavatory break. A request for a confirmation of the altitude assignment and a heading to the new fix is made. During the confusion; the altitude knob on the FCU may have been turned instead of the heading knob resulting in track and altitude deviations. ATC issues a new altitude assignment and back to the previous arrival as the Captain is returning to the cockpit.

Narrative: We were giving a descent clearance to FL240 by ATC. The captain then heard back from the Flight Attendant to go back and use the lavatory. Shortly after; Chicago center cleared me direct to PRISE intersection for the WATSN Two RNAV arrival and descend to; I thought; FL220 even though we were on the VEECK One arrival. At the same time the FA who had entered the cockpit was asking me a question. I tried to read back the clearance but got it wrong because I was unfamiliar with the new arrival and at the same time tried to get a read back of the altitude. I don't remember clearly but I think I read back FL220. I also tried to get a heading while I figured out what the new fix and arrival was. It took a while but I got a heading while I searched for the arrival. This was happening while the Captain was buzzing to reenter the cockpit. I dialed in the new heading and then talked to the captain to let him back into the cockpit. As he came in and I was passing through some altitude below FL240 center said 'I'm not sure what you're doing but descend to FL220.' I then looked up and saw 310 set in the alert window. I then redialed down to FL220. When I tried again to clarify our new RNAV arrival; center cleared us back onto our original fix and on the original arrival. I then thought about it as we made the arrival and wasn't sure if something had happened or not. Looking back I think I might have moved the altitude dial when I meant to move the heading bug. Also I am not sure about the altitude given by ATC. On the ground I let the captain know of my concerns and suggestion to write an ASAP.I should have not moved the altitude alerter until ATC gave me a more affirmative answer to my query about my read back. When the captain called to reenter the cockpit I should have momentarily ignored it while stopping my decent to clarify the altitude clearance. ATC should have given me a heads up of a clearance change before giving me the new clearance. It was too much information to all of a sudden be given the new arrival; the new fix; and new altitude at the same time. It should be easier to clarify clearances. I've noticed often times when I make a query it takes a while for ATC to reply back if at all.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.