You shall provide detailed informations about the error you are talking about, possibly including a verbose output generated by the console.
However, to retrieve iOS (iPhone) based payloads, please open Metasploit and type "search payload ios", you will get an output like this:
where line 6,7,8,9,10 and 11 are enumerating various iOS based payloads with different archs. Further, you must remember that iPhone based payloads require your device to be jailbroken, otherwise your experiment will fail due to Apple Security Policy.
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