Uploading Voicemail

I have a  27-second, 4.67 MB WAV file I'm trying to upload as our voicemail message but, for some reason, Comcast isn't enabling me to upload it as a personal greeting. 

When I click the green check button, it loads for a moment, then provides the vague answer, "Please select a valid WAV file."

Does anyone have any additional information or even how to actually contact Comcast Support? 

Thanks