Simba not working in Tekong?

Hi guys my bf just enlisted today (school 4) he's using Simba and apparently he can't connect to the wifi or use data at all (he used his friend's hotspot to text me). His sergeant also told him that Simba cannot be used and must either get M1/Singtel/Starhub... Planning to get Singtel Esim so that he can call and text 😢😢 But I saw quite a few posts on here that Simba shld work fine eh?? Anyways if he activates Singtel esim will he be able to connect to wifi and everyth? I miss him lolol and i want to talk to him 😭 Pls help soldiers thank you 🙏🏼