Openstage 20E Siemens IP Phone change to SIP

I am looking for a skilled freelancer who can help me change the operating system of my Openstage 20E Siemens IP Phone to SIP in order to work with Asterisk PBX. Key Requirements: - Experience in configuring IP phones and working with Asterisk PBX - Proficiency in uploading SIP firmware to the IP phone - Familiarity with Openstage 20E Siemens IP Phone and its operating system Specific Features: - Enable voicemail, call forwarding, and automated attendant on the SIP phone Preferred Method of Communication: - Remote access to the phone for configuration - Step-by-step instructions via email for guidance - Phone call or video conference for any necessary guidance If you have the necessary skills and experience to complete this project, please submit your proposal.