Hi and welcome to the site, I’m Louie. Sorry you had to wait awhile but I’ll do my best to help.
Initially, bear with us; re-confirm and post back with the complete model number of the LG. Additionally, who is your phone network provider?
Still, the prescribed approach is to bring this concern to the attention of your network provider. VoiceMail feature is an added service by the network hence any and all issue should be addressed by them as it would be particular to their equipment including their servers.