What now

I’m 21 years old (male) I’m a CCA making around $1800- $2100 each pay period and I’m about to become regular in a few months. All the regulars at the station are telling me to either find a better job or move up in the post office because the pay will go down once I turnover and because of the amount of time I’ll have to work in order to retire. What other positions should I look at within the post office should I look at to make more money or which jobs should I go for to make more? I have no college degrees or prior experience.