If a pension is protected in MI and cannot be garnished, why can they garnish your checking once it has been deposited into your checking account? This would be for a foreclosure mortgage deficienty?

My husband and I are 56 days behind in our Mortgage payment and heading towards foreclosure. We have tried working with our bank for about one year now. However, because we are not a fannie mae or freddie mac loan and because the bank did not take any money from the government they do not follow any government guidelines other than what they are required by law. In other words, no modification and they will only consider our medical bills as hardship they will not take into consideration that we have to eat, have utilities and other bills. We are retired and my husband has a pension and social security. I have social security disablility. 2 1/2 years ago after 12 years into retirement, my husband's employer took away our health benefits and life insurance. We now utilize about 700.00 plus a month for premiums and copays which we didn't have before and find ourselves unable to continue to be able to afford our home. Additionally, we lost 40,000 a year income from my husband's consultation business when the economy bellied up 2 yrs ago. We are so confused. We have been told that the bank cannot garnishee our retirement or social security, but once it is deposited into the bank, they than can garnish it out of our account. Can someone please explain and clarify this. Thank you!