Date: 201809
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Mission: Passenger
Flight phase: Climb
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Confusion; Communication Breakdown
Second reporter function: Pilot Not Flying; Captain
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Overshoot; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action; Flight Crew Returned To Clearance
Contributing factors: Environment - Non Weather Related; Human Factors; Procedure
Primary problem: Human Factors

Narrative: On our climb up to our Departure assigned heading of 7;000 feet; ATC advised of a Cessna traffic at our 11 o-clock doing circles in the vicinity and at a similar altitude as us. We reported the Cessna in sight and continued visual separation.We were then assigned an altitude of 15;000 feet. As we continued to climb; ATC assigned us a left turn to a heading of 310 degrees. We concluded that this new heading was in conflict with our previous traffic due to the aircraft maintaining a continuous climb and circling pattern. The Captain proceeded to advise of the conflict yet ATC disregarded with no response.ATC then issued a new clearance for a continued left turn to a heading of 260 degrees alongside an amendment of maintaining an altitude of 12;000 feet.As the Captain advised ATC again of the traffic conflict; he told me to take the turn slowly in order to maintain visual separation and we proceeded by doing so in increments to avoid the traffic which was in proximity to nearby clouds.As we cleared the traffic; the Captain reminded me that the controller wanted 260. I misunderstood and set a new altitude of FL260; when what he meant was that of a heading of 260 degrees.I recalled that ATC had mentioned 12;000 [feet] previously and asked the Captain for confirmation. As he did so with ATC; we were in the midst of passing 12;000 feet. The Captain immediately took control of the aircraft and descended back down to 12;000 feet from an altitude of roughly 12;600 feet.We communicated what had occurred with ATC; and once again; we were disregarded and shortly after passed on to another agency.What we should have done differently... We should have advised ATC 'unable' on the conflicting assigned heading [and] confirm immediately what is being issued prior to setting new altitudes; headings; or airspeeds. We should have divided the workload and confirmed with each other instead of fixating on the problem with the nearby conflicting traffic.


Second narrative: On climb out of ZZZ; we were told to maintain visual separation with a Cessna traffic that was on our left hand side. We were climbing to 15;000 feet when the controller told us to turn heading 310. That heading would have taken us direct to the traffic; so I advised ATC; but he did not respond. A few seconds later; he cleared us to fly heading 260 and maintain 12;000 feet. That heading would have taken us towards the traffic; I advised ATC and told the First Officer to take the turn slowly. So; we broke the turn down in increments to avoid the traffic. When we cleared the traffic I reminded the First Officer; who was Pilot Flying; that the controller 'wanted 260'. I should have said '260 HDG'; because the First Officer understood it as an altitude and immediately dialed 26;000 feet with the altitude selector. Since we lost the assigned altitude; I asked the controller which altitude he needed us at; and he said 12;000 [feet]. Unfortunately; we just busted through that altitude. I took controls and [descended] to 12;000 [feet]. I think at the highest we were was at 12;600 feet. What should have been done differently? [We should have told] ATC unable to take that heading instead of taking the turn slowly; that way we would have reduced our workload in the climb. [We should] be more specific; using the word 'heading' when describing a heading; to distinguish it from an altitude.


Synopsis: EMB-170 flight crew reported miscommunication led to overshooting a crossing restriction.