Hi,
1. Unfortunately that is not a current feature available in Survey at the moment. Our development team is working on an updated Survey tool that will allow this type of linking. We do not have an ETA for the release but it should become available in the next few months. For now, if possible, we suggest adding a "full name" question in your survey that asks for the name of the customer service representative. However, this relies on callers remembering the representative's name. If you do use the "full name" question, you can then use the filter tool to filter by customer service rep.
2. Can you clarify what you mean by files? If you're referring to audio files, then the limit is more about the size of each audio file. It can be up to 1.0 M in size. Please let us know if you're referring to other types of files.
3. The contacts section is for outbound campaigns, so if you wanted to send calls out to some people. Here you can add recipients individually or upload using a CSV file before creating an outbound campaign. If you are interested in outbound campaigns or contacts, feel free to look through our FAQ documentation here
http://survey.plumvoice.com/admin/docs.php?dest=faq under "Data Collection" section 4 "Outbound Campaigns".
Regards,
Plum Support