Hi Sachin,
Refer note Note 672719 - FAQ: Release strategies in the service which explains:
The field selection keys only work on item level, not on service level. Thus, the fields on the service specifications screen remain ready for input. You can prevent the change of the fields after the release of the purchase requisition as follows:
- You can use indicator 1 for not chnaging but as you told you do not wnat to use it so you have to contact your abaper for exit EXIT_SAPLEBND_001 user exit for release strategy PR'
Regards,
Priti.