Default Service contract in service notification

Hi Experts,

Also i have contracts "A & B", in both contracts I have assigned that equipment in technical object.

Now when I am creating a service order by entering Equipment details, it is also creating a notification in the background in which Sales document type field it is taking by default contract "A" and also it's not allowing me to change it.

Please advice, what can be the issue.

Thanks and regards

Sameer