However, the incompetence of Vinted’s staff is stratospheric…
I am forced to send them this with every message:
IMPORTANT – READ CAREFULLY BEFORE RESPONDING 
DO NOT SEND A GENERIC OR AUTOMATED RESPONSE.
READ, ANALYZE, and UNDERSTAND the situation BEFORE answering.
EVERY detail in my request MUST be considered. A SUPERFICIAL RESPONSE WILL NOT BE ACCEPTABLE.
REMINDER: This conversation is recorded and VISIBLE TO YOUR SUPERVISORS.
I am a HIGHLY EXPERIENCED seller on Vinted. You are not dealing with a beginner. Handle this issue with SERIOUSNESS and COMPETENCE.
Or this:
SUBJECT: FORMAL NOTICE – Malfunctions and Contractual Shortcomings 
To the management of Vinted,
I hereby FORMALLY PUT YOU ON NOTICE to take responsibility for the numerous malfunctions observed on your platform, which are causing direct harm to users. 
Your systematic refusal to acknowledge certain anomalies and to propose appropriate solutions constitutes a breach of your contractual obligations.
It is UNACCEPTABLE for your customer service to hide behind automated responses without considering the concrete facts.
I SUMMON you to implement the following measures within 48 HOURS:
A clear and effective dispute resolution process.
Direct access to a competent decision-maker.
Serious and individualized handling of complaints.
Failure to provide a concrete response within the given timeframe will compel me to take the following actions:
Referral to the competent authorities (DGCCRF, consumer ombudsman, consumer defense associations).
Legal proceedings for breach of your contractual obligations.
Public exposure of your service’s failures.
I REQUEST to be put in contact IMMEDIATELY with a QUALIFIED MANAGER and not a standardized customer service.
Response time: 48 hours.