Invalid MMI Code: What It Means and How to Fix It

Last checked: 8 September 2026

An “invalid MMI code” or “connection problem” message means a dialler request did not complete. It does not tell you one definite cause and is not, by itself, evidence of hacking. Check whether ordinary calls work before changing anything else.

Follow these checks in order

1. Confirm the purpose and spelling. Use the exact command in your provider's current instructions. A missing hash, extra star or copied space can change the request. Do not add punctuation suggested by an unrelated online post.
2. Use the built-in Phone app. Enter network commands in the normal phone dialler, not WhatsApp, a meeting app or a business softphone.
3. Choose the intended SIM. A work SIM and personal SIM may have different providers and service permissions. A data-only travel eSIM is not necessarily the line that handles calls.
4. Check ordinary service. If normal calls also fail, check that the SIM is enabled and the phone has service. Restart when convenient, check for an outage and contact the provider if calling still fails.
5. Try the supported settings menu. For call forwarding, use the handset's Call Forwarding or Supplementary services menu if available. An unavailable menu is useful information for support.
6. Ask the provider to check the account. Give the exact error, handset model, software version, selected SIM and the service you are trying to use.

These steps narrow the problem; they are not a promise that one trick will fix every handset. Android allows carriers to configure support for individual supplementary services. A standard-looking command can therefore fail on a particular service.

If only forwarding commands fail

Ask whether the plan supports the required divert, whether it is enabled on the account and whether the destination is allowed. Mention if you are roaming or using Wi-Fi Calling. Let the provider choose the appropriate network test. For the supported code forms and their effects, see call forwarding codes UK.

If *#06# does not display an IMEI

Use the device settings instead: Settings > General > About on iPhone, or Settings > About phone on many Android devices. The IMEI guide also covers finding identifiers when the phone is unavailable.

What to avoid

Do not factory-reset a working phone, delete an eSIM or erase all diverts just because one command fails. Those actions can create a second problem without explaining the first. If support recommends a change, ask what it affects and how to restore service afterwards.

A useful message for your provider

“My [phone model and software version] shows [exact error] when I request [service] on [work or personal line]. Ordinary calls [work or fail]. I am [in the UK or roaming] and [using mobile coverage or Wi-Fi Calling]. Please confirm whether this account supports the service and the correct way to manage it.”

Send account details through the provider's verified private support channel. Keep IMEIs, mobile numbers and screenshots out of public posts.

Frequently asked questions

Does an invalid MMI error mean my SIM is faulty?

Not necessarily. The request, selected SIM, service support or network connection may explain it. Check normal calling and ask your provider to investigate before replacing the SIM.

Should I erase all call diverts to fix it?

Only if your provider confirms that this is the intended action. It can remove voicemail routing and does not establish why a command failed.

Can I use settings instead of a code?

Often, where the handset and provider expose the service. Menu names and available options vary; an unavailable setting should be checked with your provider.

Sources

• Android: carrier-controlled supplementary services
• EE: alternative forwarding setup methods
• EE: finding an IMEI in settings

Related guides

• Latest business phones
• Compare phones for your team
• UK phone codes explained
• Call forwarding codes and settings
• Find your IMEI with *#06#