Have you followed their Complaints procedure?
11.2
We hope that you are happy with the use of the Service and Sites. If, however, you have a complaint, you can follow the following procedure:
STEP 1: contact Support and provide as much detail about your complaint as you are able to. Our customer service team will do their best to respond to you within 24 hours of receiving your complaint acknowledging receipt. Our customer service team will then respond to you setting out our full response. Such response will be our final decision on the matter.
STEP 2: If our customer service team cannot resolve the complaint to your satisfaction and the complaint relates to a gambling transaction (for example the placement of a bet or wager, the grant of a bonus, account management, or your ability to access funds or winnings), you may refer the dispute for independent dispute resolution free of charge.
If you exhaust our internal complaints procedure, or your complaint has not been resolved within 8 weeks of you having made it, we will send a notification to you setting out further details as to the process to follow to do so.
Our third-party dispute resolution provider is IBAS and can be contacted at:
adjudication@ibas-uk.co.uk. For further details visit IBAS' website at:
http://www.ibas-uk.com.
You should note that IBAS may reject your request if it considers it to be groundless or malicious, or if you have not undertaken Step 1 of the complaints procedure above.
You acknowledge that we are required by regulation to provide information about each dispute referred to IBAS to the Gambling Commission.
You are entitled to receive a copy of the above procedure on request or upon the making of a complaint.
Alternatively, if you remain dissatisfied with the resolution of your complaint after interacting with our customer support team, you may refer to the EU's Online Dispute Resolution Platform (the "ODR"). For more information please visit their website here, and follow the guidance provided to log your complaint.
Neither IBAS' or the ODR's decisions, nor our response to your complaint, precludes you from bringing a claim against us in accordance with Section 13 below.
13. GOVERNING LAW
We shall do our best to resolve any disputes between us. Any disputes shall be subject to the laws of England and Wales and subject to the exclusive jurisdiction of the courts of England and Wales. However, if you reside elsewhere in the European Union, you still have the benefit of any applicable rights under the laws of, and the right to bring an action before the courts of, your country of habitual residence. Nothing in this Section shall limit the right of TSG to take proceedings against you in any other jurisdiction, and if TSG commences proceedings in any one or more jurisdictions this does not preclude it from commencing proceedings in any other jurisdictions.
https://www.pokerstars.uk/tos/