International Voice and SMS Guidelines
Reaching customers and colleagues around the world is one of the core promises of a cloud-based communications platform. But the reality of international telephony is that not every destination plays by the same rules. Regulatory bodies, local carriers, and government mandates can restrict or outright block voice and SMS traffic in ways that are largely outside any provider’s control.
This article outlines the countries and regions where calling or messaging through Revenue.io is currently restricted, along with the reasons behind each limitation. Some restrictions stem from a government’s regulatory framework, others from carrier-level enforcement, and some from country-specific rules around how VoIP traffic can interact with local phone networks.
Understanding these restrictions upfront helps you set accurate expectations with your team, plan your outreach accordingly, and avoid confusion when traffic to a specific destination doesn’t go through as expected.
Voice Restrictions
Mainland China
Due to strict traffic profile monitoring by local network operators meant to reduce telemarketing and unwanted calls to Mainland China, VoIP calls to Mainland China are not allowed.
Iran
Due to additional requirements enacted by the regulatory body in Iran, voice calls and SMS/MMS traffic to Iran is not allowed and will be blocked by carriers.
Cuba
Due to regulatory requirements, voice calls and SMS/MMS traffic to Cuba is not allowed and will be blocked by carriers.
Syria
Due to regulatory requirements, voice calls and SMS/MMS traffic to Syria is not allowed and will be blocked by carriers.
Restrictions on Domestic calls in India
Calls will not route outbound to India if they are made from an Indian number (+91). This is due to increased regulations and enforcement by the Telecom Regulatory Authority of India (TRAI) which restrict mixing international VoIP and local PSTN traffic.
Messaging Restrictions
Turkey
As of April 1, 2026, all international A2P SMS messages containing URLs sent to recipients in Turkey are blocked by local operators. Turkey’s Information and Communication Technologies Authority (BTK) implemented this regulation to combat fraud in communications.
If your messages do contain URLs, your options depend on whether you have a local Turkey business entity
- With a local Turkey entity: You can continue sending URLs in SMS by securing a direct contract with Posta Güvercini (a local messaging platform), authorizing them as your service provider via the Turkish Message Management System (İYS), and working with our Support team to finalize the setup. Until that process is complete, URLs must be removed from all messages to Turkey.
- Without a local Turkey entity: URLs, hyperlinks, and shortened links must be removed from all SMS templates and messages sent to Turkish recipients. Any international message containing a URL sent to recipients in Turkey will be blocked by carriers and could be subject to fines by operators.