Start by reducing the duration of each pump session. For example, if you need 20min to clear your boobs, pump for 10min instead. Do this for 3-5 days to condition your body to produce less milk. Then extend the time in between pumps. So if you've been pumping 3hrly, change it to 4hrly. Do it for 3-5 days before extending further and then finally dropping pump sessions. You can do it faster if you want and if your body is able to adjust accordingly. This method is proposed to reduce the discomfort and potentially blocked ducts.
Start off by dropping one pumping session at a time. Try to stop one pumping session every 3-7 days. For example, in a day you usually pump 3 times; drop the first session on day 1 (while pumping as usual for the other sessions), the second session on day 4, the third session on day 7, etc. This will give your body an indication to stop producing milk. This website offers some other good tips on how to wean off if you have been exclusively pumping: http://exclusivepumping.com/weaning-from-the-pump/
One of my friends did that by increasing the amount of time between pumps. She was pumping once every 3 hours. So she changed to once every 3.5 hours (she tried 4 hours first but felt engorged). Gradually, increased to 4 hours etc. That led to dropping one pump session and another and ultimately, weaning from pumping.
from my experience will be cutting down the no. of pumping sessions and duration slowly..