Dutch Phone Relay

How my Dutch 06 number keeps working on my iPhone while the SIM stays home in the Netherlands.

Overview

A Redmi Note 7 with the Simyo prepaid SIM sits plugged in at home on Wi-Fi. It relays texts and forwards calls; everything else runs on the iPhone.

What	How
Send texts	“NL SMS” shortcut on the iPhone → SMSGate → Redmi
Receive texts	Redmi → SMSGate webhook → ntfy notification
Make calls	MyTello, showing the 06 number as caller ID
Receive calls	Simyo call forwarding → CheapConnect 085 number → Groundwire
Remote access	Tailscale + adb over the network

Credentials (SMSGate login, ntfy topic, SIP password) are deliberately not on this page. They live in my password manager.

01 Sending texts

iPhone shortcut→api.sms-gate.app→SMSGate on Redmi→SMS from 06

Run NL SMS from the home screen or Siri, enter the number as +316… and the message.
The shortcut sends POST https://api.sms-gate.app/3rdparty/v1/messages with basic auth and the body below.
SMSGate runs in cloud mode with Notification channel: SSE Only. The Redmi runs a Chinese MIUI ROM without Google Play Services, so Google push isn't available.

{ "textMessage": { "text": "Hello" }, "phoneNumbers": ["+316…"] }

Check a message's status with GET /3rdparty/v1/messages/<id>, or in the SMSGate app under Messages.

02 Receiving texts

SMS to 06→SMSGate→webhook sms:received→ntfy.sh→iPhone notification

The ntfy iOS app subscribes to a private topic on ntfy.sh. Notifications are titled “SMS from <number>”.
The webhook uses ntfy templating: ?tpl=yes&t=SMS from {{.payload.sender}}&m={{.payload.message}}.
MIUI's spam filter is set to Allow for both “Messages from strangers” and “Service notifications” (Security → Blocklist → SMS blocklist). Otherwise texts from unknown numbers and verification codes never reach SMSGate.

03 Making calls

MyTello on the iPhone, verified with the 06 number, so outgoing calls show the 06 as caller ID.
The verification code arrived through the SMS relay above.

04 Receiving calls

Call to 06→Simyo forwarding→CheapConnect 085→Groundwire on iPhone

CheapConnect prepaid VoIP with an 085 number, €8.95 a year, renews 1 November 2027. SIP server sip.cheapconnect.net, port 5080 (avoids SIP ALG).
Groundwire (€9.99 one-off) holds the SIP account and wakes the iPhone with push.
Forwarding costs €0.10 per minute of Simyo prepaid credit.

Forwarding codes (dial on the Redmi)

Action	Code
Forward all calls	`21085…` (national format, dialled as a call)
Turn forwarding off	`#21`

The GSM-style **21*…# fails on Simyo 4G, and +31 format gives “number not in service”. Android doesn't show a forwarding icon even when it's active, so a test call is the only check.

05 Remote access

Mac on Tailscale→tailnet→Redmi 100.98.25.119

Tailscale (F-Droid build) on the Redmi is set as the always-on VPN, so it reconnects after a reboot.
Network adb listens on port 5555:

adb connect 100.98.25.119:5555
adb -s 100.98.25.119:5555 shell pidof me.capcom.smsgateway

Android 10 without root turns network adb off on every reboot. Tailscale comes back, adb doesn't: someone at home has to plug the phone into a computer and run adb tcpip 5555.

Upkeep & troubleshooting

Keep the SIM alive: Simyo deactivates prepaid SIMs with no activity for 6 months. Send at least one text every few months. Credit doesn't expire.
Is the relay online? GET https://api.sms-gate.app/3rdparty/v1/devices shows lastSeen for the Redmi.
Sending fails with “No SIMs found”: MIUI's own permissions (MIUIOP 10004–10032) for SMSGate must be set to allow. The SIM sits in slot 2.
Texts don't arrive: check MIUI's blocklist (see 02), and that READ_SMS/RECEIVE_SMS are allowed for me.capcom.smsgateway.
Calls don't ring: check Groundwire shows the account as registered, then re-dial the forwarding code on the Redmi.