@Sherif Abouseda - I will assume that you are trying to downgrade to the Starter Plan rather than cancel your paid subscription altogether. If this is correct, there is currently no way to easily accomplish this yourself. You will need assistance from Miro support.

You can find the support form by following these steps in the How to contact Miro support help center article:

https://help.miro.com/hc/en-us/articles/360020185799-How-to-contact-Miro-Support#h_01F010RXA0E1S9C0WFQYX75R6C

Thank you for your support. It is near impossible to get support. 

Still trying and they just charged me for another year so I am sure that is going to be another problem to deal with.