Can I put my sim card in a Samsung sph-m840 - Samsung Cell Phones

SOURCE: How do I remove my phone number from a Samsung SPH-M500 phone?

If you have ported the number assigned to this phone from Sprint to ATT, the phone is no longer usable with your number. New owner will have to call Sprint and get another assigned, which they can do over the air.

SOURCE: Samsung SPH-A640 unlocking codes

sorry no.
the sph-a640 is a cdma phone and not compatable with sim cards

SOURCE: How and where do i insert my sim card into my

Open the back of your phone's cover. Take off the battery. The must be a small slot of small size. There may be a steel coverage, if present open and insert the sim. If what I told does not help, contact your phone dealer.

SOURCE: HI,I WANT TO KNOW WHERE IS THE PLACE TO INSERT THE

samsung instinct is a CDMA phone no sim card to use a sim card you need a gsm phone AT&T, boost mobile, companies like that use sim cards

SOURCE: Samsung sph m220. how do I remove the sim card?

That phone is a CDMA phone and does not use a SIM card. Sprint phones and Verizon phones are CDMA and do not use SIM cards. AT&T and T-Mobile use SIM cards, but are GSM phones, a whole different technology/signal. Nextel phones do have SIM cards, and some "World" phones at Verizon have SIM cards for traveling overseas where there is no CDMA, but your Samsung SPH-M220 has NO SIM card.
Just in case you want to check anyway, here is a link to the user's manual:
http://support.sprint.com/global/pdf/user_guides/samsung/m220/m220_by_samsung_ug.pdf