I took one for the team...
I successfully reserved a LIM-BOG tix on Lan Peru site... then called the USA number to pay for the reserba. Successfully... at the end of the call he said: you have 24 hours to cancel or change the ticket, after that you have to suck eggs to get us to make a change.
Seems we have proof now.
small print: pretty sure the call went to SCL but when they asnswer the USA line they access the USA computer and are limited to the fares offered on the US site - know this from a previous experience