Hi Harshita,
In case UE receives RRCConnectionReject with deprioritisationReq, UE shall consider current carrier frequency and stored frequencies due to the previously received RRCConnectionReject with deprioritisationReq or all the frequencies of EUTRA to be the lowest priority frequency (i.e. lower than the eight network configured values) while T325 is running irrespective of camped RAT. The UE shall delete the stored deprioritisation request(s) when a PLMN selection is performed on request by NAS
Message(From RRC spec):---
RRCConnectionReject-v1130-IEs ::= SEQUENCE {
deprioritisationReq-r11 SEQUENCE {
deprioritisationType-r11 ENUMERATED {frequency, e-utra},
deprioritisationTimer-r11 ENUMERATED {min5, min10, min15, min30}
} OPTIONAL, -- Need ON
nonCriticalExtension RRCConnectionReject-v1320-IEs OPTIONAL
For more please refer 36.304 cause 5.2.4.1 Reselection priorities handling