Yes, you can use a Verizon CDMA iPhone 4 with Straight Talk...I just did it yesterday.
I purchased an iPhone 4 (CDMA version) from Groupon. Groupon listed this to work on Verizon or PagePlus. I was looking for a replacement for my current ST LGL75 (Optimus Zip on CDMA).
- Paid $140 for a 32GB iPhone 4
- once the iPhone 4 arrived, I checked the ESN (MIED) to see if it was it was clean (http
/swappa.com/esn)
- Went to StraightTalk's BYOP (www.straighttalkbyop.com) page and entered the MEID on their page as well as my ZIP
- ST showed it would work on their network
- Purchased the online Activation Code for $7.50
- logged into my current ST account and selected "Activate Phone/SIM" and then "Transfer my existing ST service"
- entered the iPhone 4's MEID, selected no for LTE and no for iPhone 5 questions
- two hours later my old LGL75 dropped from the network
- on the iPhone 4 I dialed *22890 for over the air programming
- once finished, I called my home phone and the call went through
After all this was done, the phone was on the ST network (in this case, using Verizon 3G towers)
The iPhone 4 automatically had the APN programmed and I have no problem using the phone. MMS, text, and data work without issue. I was even surprised to find that I have hotspot and visual voice mail on the new iPhone 4.
So yes, if you have a Verizon iPhone 4, it will work with Straight Talk will all functions. Remember that iPhone 4 is not an LTE phone, so you will only get 3G. This should also work with 4s CDMA phones.