Collections calling after garnishment

I am currently in default on my student loans. During the time the process for wage garnishment had begun, my husband lost his job and with it more than 60% of our household income. He has not been able to find regular employment since. The collection agency continued to call after we entered garnishment wanting to put me on a payment plan to get out of default. I explained that at this time my wages were currently being docked and we are relying on family to pay our mortgage as we are unable to meet our monthly expenses on just my salary. I had 40% of the income I had when we defaulted on the loan and was unable to make payments at that time and was not willing to commit to a monthly payment plan in addition to the 15% of my salary that was being garnished in light of our situation. I explained that I would contact them when my financial situation changed as I am interested in setting up a payment plan, but without knowing whether or how much my husband would earn, I could not say what I would be able to afford. Okay, about 6 months later with my husband still out of work, I am under a 10 month contract at work plus an additional 30% stipend off my contract. I made arrangements for my salary to be paid over 12 months instead of 10 so I would have guaranteed income all year, meaning each check is noticeably smaller. After the start of the year, my boss cuts 20% from my stipend. As of now, my monthly income is less than my mortgage payment alone - we are currently earning 25% of what we made with both our salaries. My husband has joined the National Guard and has volunteered for deployment to make ends meet. I am now told that my employer is planning to cut 10% from the salaries of every employee plus require 10 furlough days.
I am currently being harrassed (4-5 phone calls per day from 2 separate collections agencies). I can NOT enter into a contract for a payment plan at this time. I have no idea what my salary will even be next year. I would say I am currently living paycheck to paycheck but that isn't even true as my salary does not stretch that far. These people are calling my house phone, my work phone, and my cell phone (pay as you go that I have to pay per call, so this is costing me money if I answer). I do not have a job where I use the phone and stopping to answer the telephone interferes with my ability to carry out my responsibilities at work. I do not give out my cell phone number and up until 2 weeks ago I received about 1 call every two weeks, used for emergencies only, but now I am going to have to keep it turned off and will not be able to answer should my family need me. I need these calls to stop. My wages are already in garnishment and there is nothing else the collection agency can do at this point other than bully me - is that correct?