Did you recently receive your PR card with new last name? I think your applied for citizenship and renewal of PR card for name change around same time.
The "decision made" might be for your replacement of pr card (Under Permanent Residence Application section) for your new last name and now it might should show "Complete" or this section might be vanished if you have received teh replacement PR card quite a while back.
Now currently your online status might show "In Process" with following lines
Under Citizenship application section):
1. We received your application for Canadian citizenship (grant of citizenship) on xxxx
2. We sent you correspondence acknowledging receipt of your application(s) on xxxx
3. We started processing your application on xxxxx
The 4th line regarding file transfer to local office has disappeared for many members in this forum including myself.
Hopefully you will get your test invite soon.