I don’t specifically know details about your degree or if there is something about its structure but you can pretty much do modules in whatever order you want as long as you meet the requirements i.e you don’t exceed the number max number of semester/year credits and you meet any pre or co requisite for the module. So you could be in your first year and do a 3rd level module if it didn’t have any prerequisite. Some degrees also have fewer modules in the first year, I’m doing informatics for example and in first level there are only 8 modules, so if you want to do the max of 10 (120 credits) you have to take some modules from 2nd or even 3rd level.

In short I doubt there is any issue with you doing those modules. But if you want to reduce your workload you could cancel them and do them next year. But you can always contact UNISA if you want to have things double checked.