Hello,
1- I don't think the call agents are working over the weekends. So, I don't think you could reach them. You can google and find out their working hours. However, you may stillhave hard time reaching them due to high volume of calls.
2- I recommend sending a CSE and askin what to do
https://secure.cic.gc.ca/enquiries-renseignements/canada-case-cas-eng.aspx
The good point about CSE is that you can keep the response as a document.
3- You don't have enough time to lawyer at this stage. You only have 5 days, so you should send some documents for now.
4- Don't worry, they won't reject for no reason. After sending some document, it may take some time for them to check your doc and make the final decision.
5- If you didn't get any response from CSE or phone call in this short period of time, proceed with including a cover letter explaining the situation.