Date: 202202
Location: ZZZ.Airport, US
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Climb
Aircraft component: Exterior Pax/Crew Door
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Flight Attendant (On Duty)
Reporter qualification: Flight Attendant Current
Human factors: Troubleshooting; Distraction; Communication Breakdown
Second reporter function: Flight Attendant (On Duty)
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR
Detector: Person Flight Attendant
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: After boarding the A Flight Attendant told me about the forward galley service door being closed but that he could see daylight in the cracks. And that he unsuccessfully tried to recycle it a couple of times and eventually the First Officer (FO) managed to get it closed correctly. He also told me he heard a ramp agent tell the pilots about potential damage to the aircraft but they said all was good. He could not quite understand the technical terms so not much info is known about this. Upon ascent both the A and I heard a sharp whistling noise coming from the forward service door so the A called the pilots who said the pressurization looked good. Upon descent though we both heard and felt a loud rumbling noise and felt vibration on our feet. We could not quite figure out which if any of the forward doors it was coming from. He called the pilots and notified them and they said they heard nothing. While deplaning a few passengers mentioned there being a very loud noise as far back as row X. We both mentioned to the pilots that passengers heard the same noise we did. The A requested maintenance but the pilots said it looked good and it was probably a piece of rubber that could make that sound. The flight to ZZZ1 was uneventful. We did tell the Operations Agent about what we heard during ascent and descent. Thankfully he called for maintenance who then said the aircraft was unsafe to fly and it was taken out of service. I was not there at the time but the A contacted me and told me the Operations [Agent] reached out to him and updated him on what was happening. It needs to be mentioned that the pilots were both commuters.


Second narrative: During boarding on Aircraft X; I noticed that the FWD Service door was not closing properly. While it was in the closed position; I could see daylight through the upper right side of the door.  I tried to cycle the door four times to no success.  The door did not feel normal in its operation. It felt more sluggish than normal. I thought this could possibly be due to the cold weather in ZZZ. I notified the pilots and requested maintenance. I verified in the flight deck that the FWD Service door was indeed showing open on their panel. The First Officer (FO) came and attempted to close the door slowly. He was able to get it closed and the light came off. No maintenance ever arrived to the aircraft.  Before the FWD Entry door was closed; a ramp agent came to let the flight deck know that they spotted a potential damage area to the aircraft. The FO mentioned he is aware of it. The ramp agent stated it was slightly different than what the FO was referring to. The FO never went outside to verify what the ramp agent observed. I did not understand the technical terms to provide further details on this issue.Upon ascent out of ZZZ; there was a high pitch whistle noise coming from the lower right side of the FWD Service door. This was also verified by Flight Attendant (FA)-C who was present at the time. This was at about flight level 340. I contacted the flight deck and was told that the pressurization is normal.  On our descent into ZZZZ; at/around 7;000-10;000 ft there was a sudden loud deep vibration that lasted all the way until landing. I felt that this vibration was coming from the FWD Main Entry door; lower right side. However FA-C stated that she thinks it is coming from the FWD Service door. I called the flight deck to let them be aware but kept it brief since we were close to if not in sterile flight deck.  Captain said that he could not hear anything. Pilots had us secure cabin at flight level 140 due to weather but never gave us the 10;000 foot chime for sterile flight deck.  Upon arrival; multiple passengers commented on the noise. Passengers seated as far back as Row X also heard the noise and made this complaint to the Captain upon arrival.  I requested maintenance in ZZZZ; but was advised by the Captain that it was 'probably a piece of rubber and it can make that kind of noise'It should be noted that both pilots mentioned they are commuting pilots and in a hurry to return to ZZZ2 to make their flights home. No maintenance ever arrived. Upon arrival into ZZZ1; I let the Operations Agent be aware of the situation. The Operations Agent called me about an hour after arrival to verify the details of the situation. I provided the Operations Agent with details from our flight into ZZZZ. About 10 minutes later the Operations Agent called me back and thanked me for the details. He stated that when ZZZ1 maintenance arrived; they instantly looked at the door and declared the aircraft not air worthy; and pulled it out of service immediately.


Synopsis: Flight attendants reported during the flight they heard a noise emanating from the area by the door and notified the Flight Crew. The cause of the noise was not confirmed.