I keep getting ORA-12514: TNS:listener does not currently know of service requested in connect. Also suppose if i try same command 5-6 time then sometime it may work

[bhaskardabhi]

[root@626fcb24f793 /]# sqlplus system/oracle@//localhost:1521/EE.oracle.docker;

SQL*Plus: Release 12.2.0.1.0 Production on Tue Sep 25 11:11:25 2018

Copyright (c) 1982, 2016, Oracle. All rights reserved.

ERROR:
ORA-12514: TNS:listener does not currently know of service requested in connect
descriptor