I have had mixed luck with IHG customer service. I just sent an email on missing points from late December, and it was resolved in a few days. When they replied with the resolution, I further inquired because it also was the final stay I needed to complete my Into the Nights promo. They responded within a day or so. So THIS exchange was good.
I previously had about 15 email exchanges with them about another problem and they were not so helpful. They always replied, but were stone deaf. One tweet to @IHGCare completely resolved it.