There are several sources available to help you, please use them in the order suggested here:
Level 1 support: Please contact your Partner.
Level 2 support: Please refer to the SLA.
Should you have any technical issues, please contact your Partner. Should your Partner not be able to assist, please contact the NFON Service Desk at +49 89 453 00 555 or +49 800 6366 555 or open a service request at support(at)nfon(dot)com.