Custom attributes assigned to a dedicated server subsciption are detached during the subscription hosting plan change or upgrade.
Such behavior was classified as the software issue PBAS-30163 and was fixed in OBAS 4.5.6 release.
To resolve the issue, please upgrade to 4.5.6 as described in How to upgrade OBAS system to the latest available version.
Hotfix for 4.5.5
If upgrade is not an option for you, below is the hotfix for 4.5.5 version.
for 32-bit OS
# rpm -Uhv billing-4.5.5-36.swsoft.i386.rpm # service hspcd restart
for 64-bit OS
# rpm -Uhv billing-4.5.5-36.swsoft.x86_64.rpm # service hspcd restart
Please note that the hspcd service restart will cause OBAS downtime for less than 5 minutes.