Stopping retirement benefits

I have not seen the ability to turn retirement benefits on and off as you are seeking.

There is a way to essentially rescind your decision to take early benefits by filing a "Request for Withdrawal of Application" SSA-521 form :
http://www.ssa.gov/online/ssa-521.pdf

With this you can "undo" your decision to receive early benefits, but you'll have to repay all the benefits you received (but without interest).

Here are some details on this :
http://www.kiplinger.com/features/archives/2008/02/krr-tactics-for-takin...

Here are a couple other links that may be useful for this :
http://www.ssa.gov/pubs/10069.html
http://www.ssa.gov/retire2/retcalc.htm