Dear XXX，
Thanks for your feedback. If I have caused any confusions, sorry about that. Let me clarify it as follows / Could you please explain more about...(the point here is to clarify the issue/situation).
I thought we were working together to (save money and time) for the company. Please be assured that I've made, and will make every effort to (support you/your division/the project etc.). Next time when you (need something), could you please (explain it a bit more)? It's kind of hurting when somebody's efforts are denied without (an explanation), isn't it?
Again thank you for your feedback, and I look forward to your reply.
Kind Regards,
XXX
- That's something similar in structure that I wrote to a manager at a partner's company who complained harshly about a mistake I made (due to the wrong information I got). Later on I actually developed a very good working relationship with him. Hope it's of a bit use to you, depending on the relationship and the situation though.
