There are 3 ways in which you could configure frame relay fragmentation. They are:
1.Using the "frame-relay fragment" command, as per the FRF.12 fragmentation.
2.Using the FRF.11 fragmentation. This method is not recommended for use with Voice over IP (VoIP).
3.Cisco Proprietary fragmentation using the command "vofr cisco"
The 3rd options could be the solution for your query.
For more details on this, please refer to the following document:
Configuring Frame Relay Fragmentation
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fwan_c/wcffrely.htm#1060792
For more details on the 3rd option give above, you could refer to:
Cisco Proprietary Voice Encapsulation
http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_configuration_guide_chapter09186a00800ca6a9.html#xtocid232909