Change the payment terms - Error while trying to save service order

Hi,

I am facing an issue with Terms of payments while saving a service order in web ui "Please Change the Payment terms".

generally we can save service orders with any of the listed payments terms, however I am facing this for a particular customer and with specific payment term only.

if anybody has any idea about this issue, your help will be much appreciated and points will be rewarded.

Thanks

Rajesh Mahajan