Credit for improvement in customer service level should go to the Supply Chain team.
Responsibility for improving customer service level rests with the supply chain team, comprising Planning, Procurement, Manufacturing, Logistics and Customer Service. If there is an improvement in service level, it means additional sales for the company, for which full credit should be given to the team.
At the same time, it is important that the team takes full responsibility for any drop in service levels, resulting in loss of sales. No room for excuses like under-forecasting, vendor default, disruptions, etc.
If the team is willing to take responsibility for underperformance, it truly deserves full credit for improvements in this important customer metric.