Per thread, which referenced http/www.phonenews.com/straighttalk-targets-pageplus-will-launch-verizon-byod-service-on-tuesday-22711/ , you can pay for a network access code (NAC) now, no SIM card needed. Check both links bc PagePlus, a competitor to Walmart/StraightTalk, is discussed as well.
The NAC service began March 26th, so Inzone's February post was right on.
ALERT - StraightTalk.com shows different coverage for Android (lots less) vs non-Android phones per map linked from FAQs. Here's the map link: http/tinyurl.com/bl6khwk Likely related to data, but I'm not certain if the less coverage is for VZW-branded data phones or ST data phones (I'd hope that the VZW phones would receive all of VZW coverage; I don't know who covers Straight Talk phones with data access, maybe Sprint?).