ADSL and ADSL2+ are the same price, so the logical compensation would be the difference, which would mean because it is no difference there would be nothing to compensate.
1.5Mbps is the exact minimum speed before Telstra will investigate the speed... 1Mbps is the minimum that the ACMA state is acceptable....
Since it seems this is the first time you have been bothered enough by the speed to follow up on it, it is also hard as it is impossible to say if it has always been as slow as 1.5 or has dropped to 1.5Mbps because of other issues (such as distance from the exchange, congestion or line faults, or noise... etc), also if you are over 3km from the exchange you are pretty much going to find that there is no difference between ADSL and ADSL2+... sometimes at those distances ADSL1 is actually faster.
That being said, generally speaking the first step would usually to be to deal with the company in question, so following normal escalation process you'd try Telstra's billing team, followed by complaints then it would be up to you, you could try take it to the TIO after complaints.
1.5Mbps is the exact minimum speed before Telstra will investigate the speed... 1Mbps is the minimum that the ACMA state is acceptable....
Since it seems this is the first time you have been bothered enough by the speed to follow up on it, it is also hard as it is impossible to say if it has always been as slow as 1.5 or has dropped to 1.5Mbps because of other issues (such as distance from the exchange, congestion or line faults, or noise... etc), also if you are over 3km from the exchange you are pretty much going to find that there is no difference between ADSL and ADSL2+... sometimes at those distances ADSL1 is actually faster.
That being said, generally speaking the first step would usually to be to deal with the company in question, so following normal escalation process you'd try Telstra's billing team, followed by complaints then it would be up to you, you could try take it to the TIO after complaints.