Do you have enough points to make the 1 BR in addition without borrowed. If so, just make it online then cancel the 2 BR online. If you have banked, borrowed points you can either then make a second 1 BR reservation using the banked/borrowed points and cancel the first 1 BR OR get MS to reallocate the points. It's really not as complicated as it sounds and you have control, usually much easier and quicker than calling in. An alternative is you can check to see availability then if it is available for the 1 BR, cancel the 2 BR and reserve the 1 BR yourself online. Calling may be the best way if it's something that might not be easily available but just to give you an alternative. Just make sure you're not within 31 days or so.Thanks. I assume excess points will be returned.