This guide is for a mobile SIM installed in a router, MiFi or LTE/5G modem at a customer site—not a SIM normally used in a handset.
The question
“How can I check the data balance on a SIM in a remote router and recharge it without visiting the customer site?”
Answer first
Link the router SIM’s cellphone number to the network provider’s app or web account before leaving the site. That gives you the most dependable way to check the network-side balance and buy data remotely. Treat the router’s USSD feature as a backup because support varies by model and firmware.
Check balance
Link/manage the router SIM in the MTN App; *136# is the common prepaid balance route when the router supports USSD.
Recharge / buy data
The MTN App can buy bundles for your own or another MTN number. *136*2# opens prepaid bundle buying on a USSD-capable router.
Official source: MTN AppCheck balance
Link the data-device or router number in VodaPay/My Vodacom and view its balances remotely. A compatible router can also send *135#.
Recharge / buy data
Buy for the linked router line in VodaPay/My Vodacom, or buy for another Vodacom number. *135# also provides bundle options where USSD is exposed. Some Home Internet products are restricted to Vodacom-approved routers, so confirm the exact product first.
Official source: VodaPay account guidanceCheck balance
Use the MyTelkom App or Web Self Service for a registered product. Telkom also lists *188# from the SIM or WhatsApp 086 160 1700 from any network for balance checks.
Recharge / buy data
Buy bundles through MyTelkom, Web Self Service, a banking app, *180# on compatible hardware, or WhatsApp 081 160 1700 from any network.
Official source: Telkom balance and bundle guidanceCheck balance
Use the Cell C App or website Self Service for the router SIM. If the router exposes USSD, use *101# for a summary or *147# for the menu.
Recharge / buy data
Buy a bundle online by entering the router SIM number, or use the app. Compatible routers can use *147#; a voucher can be loaded with *102*voucherPIN#.
Official source: Cell C data bundlesCheck balance
Manage the service in your Rain account. Rain is account/subscription based, so the handset-style USSD and voucher workflow does not apply.
Recharge / buy data
Manage the plan, payment method and any applicable usage/spend controls in the Rain account rather than loading prepaid airtime.
Official source: Rain accountKeep the router SIM number, ICCID, network, tariff and router model in your customer record. Provider setup may send an OTP by SMS, so complete linking while you can read the router SMS inbox.
Register the line in the official app or web portal and confirm that its balance is visible from a different internet connection before leaving the site.
From off-site, check the balance and make a small top-up or bundle purchase. Keep a “buy for another number” route in a banking app or operator portal as a backup. The purchase may still require a login, OTP or payment confirmation.
Managing ordinary prepaid SIMs one by one can become fragile at scale. Business IoT/M2M or managed-connectivity services may provide a central dashboard and stronger operational controls. Compare the product terms carefully: a fixed-LTE or Home Internet SIM may be tied to a location, tariff or approved router and may not behave like an ordinary prepaid SIM.
Yes, on compatible hardware. 3GPP TS 27.007 defines AT+CUSD for USSD. A typical balance request is conceptually:
AT+CUSD=1,"*136#",15
Do not treat that line as universal production code. First detect the modem and AT port, confirm registration, test AT+CUSD=?, handle multi-step sessions and character encoding, set timeouts, redact account data from logs, and allow only approved USSD strings.
Reviewed by Riccardo Vallaro, Telecom & Mobile Services Specialist
Last reviewed: 12 July 2026
Sources we check: Official MTN, Vodacom, Telkom, Cell C and Rain self-service information, plus 3GPP TS 27.007 for modem USSD. Router menus and modem firmware vary, so test the exact model before deployment.
Why trust this: Guides are based on public operator pricing, USSD flows, official support pages, and South African prepaid user needs.
Found outdated info? Send a correction.
Usually yes. The most reliable method is to register or link the router SIM number in the network provider account or app. You can then check the network-side balance and buy data remotely, even though the SIM remains inside the router.
No. A router traffic counter measures bytes that passed through that device. It may reset, omit earlier usage, or disagree with network billing. Treat the provider account or USSD response as the authoritative remaining balance.
Sometimes. A compatible cellular modem may implement the 3GPP AT+CUSD command on a serial AT port. Many consumer routers hide that port, omit USSD in firmware, or use vendor-specific APIs, so a universal script cannot safely support every model.
USSD support depends on the modem, firmware, network mode and operator. Data connectivity alone does not prove that the router interface or modem exposes USSD. Use the provider account route as the fallback.