"You should first get some cash. Enough to cover both a burner phone and a burner SIM, + double
that and a little more (assuming you got enough money, or replace the other half with some drugs).
Find a homeless guy, ask him to go buy the burner phone and SIM and as reward he would get this
money (should be more than what the phone and SIM costs or he'd just steal)/drugs(if he's an addict)
in return. Activate SIM and phone outside a 50 mile radius of any place associated with you. Make
the calls there too. When you're done, there will most likely be money left on the SIM, so give it
to another homeless guy and have him obfuscate trails. The phone's can be bought at any electronics
store, and the SIMs, are easy to find. Kiosks will usually advertise a vendor like Lebara or the like.
Hope this helps, and watch out for CCTV.
To briefly summarize the comments below:
- Leave your own phone at home and turned ON
- Travel by bike if possible, otherwise use public transportation (watch out for CCTV)
- Do not travel with your own car (stolen is O.K.) to avoid CCTV and ALPR (Automatic License Plate Registration)
A little extra (Apply if necessary):
Depending on your threat model/adversary's capabilities or if you are currently
facing/suspecting any physical threats, I would strongly recommend to employ
surveillance detection and surveillance evasion if needed. This way you can be
sure your adversary cannot confirm you were at a specific place and time when the
calls were made.
You don't know if the ISP/NSA/etc., or your adversary is recording the calls and
to avoid voice-recognition or voice-analysis, I recommend getting a device that
will change your voice when you speak.
After use, wipe the phone, its battery + SIM and clean those with a piece of cloth
or similar(including the phone's interior which is immediately accessible when you
pop off the back). It is best to avoid having your fingerprints or other DNA, on the device.
If you need to transport the phone outside of the 'secure' location, take out the battery and
SIM and travel with that. If you have it, put it in a faraday bag. Re-assemble only at 'secure' location.
I'd add is to never bring your real mobile phone with you for any of these steps as it can reveal your location
and help correlate the anonymous call to you. In clandestine operations always leave your personal electronics
at home - consider using public transport for the op as well so that any CC cameras can't capture your car's number plate.
Good point. Don't know why I didn't include that. Important though is, leave the phone at home and turned ON. So if the
carrier or the police look at connection logs, it would appear as if you were home the entire time."