[opinologo]

Iremember doing exactly this kind of hack for a small telco in Bueno Aires. Extel. Around the year 2000.

In most cases it was not much more difficult than what OP described.

[iamflimflam1]

I worked on some software that was used by telcos around that time - you were probably hacking our dongles :)

[iamflimflam1]

Even more amazingly - that software I worked in is still being used and sold. Probably still has some of my ropey old code on it…