Rear driver side passenger door

[Bear123]

Hi, new Passat owner. Have a 2014 estate, ideal for the kids and dogs. Well, first time kids went to get in, they said the door would not open. I had a look and tried the handle. No tension on the handle at all. Door would open from the inside so did that for the day. Got home and thought I would have a proper look, mistake!! I stupidly thought that maybe the child lock was playing up so turned it off and on few times, sprayed it with WD40. But then shut the door whilst the lock was on. Now can’t open the door, either from the inside or out. I have looked around and saw mention of banging the door near the handle sometimes gets it working. Has this worked for anyone, when the handle has no tension? Any other ideas? Also had anyone paid to have this fixed and if so how much did it cost? Thanks.