Once you have set the topiclock on in your channel, check the flags of those who have access. Be sure only those you want to have access to changing the topic have the t flag in their access flags for your channel. To check who has what flags in your channel, use the command:
/cs flags #channelname list
Example: /cs flags #Joes_Hideout list
/cs help flags
for a list of channel flags and what they do and how to set them.