This will depend on your exact age and on the service’s policy. No matter what age you are, what is most important is that you get the support you need. All services should discuss this with you and support you to access the support of a parent/ legal guardian or someone else appropriate if possible.
If you are over 16, you may be able to have counselling if the service provides this without a parent or legal guardian being with you or consenting to you having counselling. Many services however will only provide counselling to persons under 18 if they have the consent of a parent or legal guardian. All services should discuss their policy with you around this and help you to get the support you need.
If you are under 16
If you are under 16, then a service will require parental/ legal guardian consent for you to have a counselling session unless the circumstances are exceptional. The service should discuss this with you and explain how important it is for you to have support.