Service Contracts can have a Currency Code filled out but the value that you see on the contract are only ever in LCY. These values are converted to the FCY when the Service Invoice is generated. This means that the values on the Service Invoice fluctuate based on the Currency Exchange Rate. It should be possible to specify a Contract Currency and Invoicing Currency so that the value that are entered on the Service Contract are the same values that are put on to the Service Invoice.

If you have an agreed price with a customer for a contract it should not fluctuate based on exchange rates, the existing functionality is not consistent with the Sales & Purchase Price functionality where values can be entered in FCY.