However, I do have one tiny nitpick to make: It's not possible to make a collect call to an "untraceable" cell phone. In fact, I'm tempted to say that it's not possible to make a collect call to any cell phone, but I'm not 100% sure that this is true. I do know for a fact, however, that to be able to accept a collect call, the recipient has to have some sort of an account with a phone company and receive a monthly bill. A collect call to a pay-as-you-go cell phone (which I assume is what you mean by "burner cell") would not go through; this I know for an absolute fact.
Also, to all writers in general: If a phone is not answered and not hooked up to an answering machine/voicemail, it will not ring indefinitely if the caller does not hang up. What actually happens, 99% of the time, is that it will ring 20-25 times and then a phone company recording will come on saying that the party is not answering and then the call will be automatically disconnected. Sometimes if you call into a large system with a lot of extensions and you try to connect to one of the extensions it will ring indefinitely, but that is the exception rather than the rule.