Service tax exemption on exports for eou if exports are set

Dear all,

Its very urgent, please reply on this issue... A software company, which is a 100% EOU, claims exeption for service tax on exports. This company exports to a another company in united states and from the same company it imports some software. As per the Exports of services rules, service tax exemption on exports can be claimed only if convertible foreign exchange is received. If the company set off exports against imports and no foreign exchange is received can still service tax is exempted? Please reply.... Please provide section, rule, notification in this regard if any...

Thanks in advance