removing seat belt plastic cover

I have a 2006 Ford Focus II (europe).
Recently I'm having a problem with a rattling noise coming form the interior B-pillar trim where the seat belt hanger is.
In order to eliminate this noise I tried to remove this seat belt plastic cover but I failed because I'm afraid to break something (plastic clips maybe..)
Could someone please give me instructions how to safely remove this plastic cover?
Thanks in advance!
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