Custom Infotype Field Name change

I have created a Custom Infotype with Date of Origin fields. Now the client requirement is to have the field names as follows

label (Date of Origin) to be u2018Contract Dateu2019 for the 1st date.

The 2nd date should be u2018Payment Date1u2019 and the 3rd date should read u2018Payment Date2u2019.

How can the above changes be made to the label??

Regards

SAI