How to Identify Disconnected Phone Numbers Automatically

Overview #

Disconnected phone numbers are automatically identified using phone validation APIs that return Phone Activity Scores and line status data. Trestle’s Phone Validation API validates phone numbers and provides a Phone Activity Score to identify disconnected numbers along with carrier, line type, and prepaid status.

Phone Activity Score Explained #

Trestle’s Phone Activity Scores range from 0 to 100:

• Score of 100: Consistent activity in the last 12 months
• Score of 70+: High confidence the phone is connected
• Score of 30 or below: High confidence the phone is disconnected or no one will answer
• Score of 0: Disconnected number or no activity seen in the past 12 months

API Response Data #

Data Field	Description	Purpose
Phone Activity Score	0-100 rating for phone activity	Identifies disconnected or inactive numbers
Line Type	Mobile, landline, fixed VoIP, non-fixed VoIP, toll-free, premium, voicemail	Dial and route calls appropriately
Carrier	Current service provider	Optimize delivery by network
Is Valid	Number syntax validation	Catch formatting errors
Is Prepaid	Prepaid line status	Risk assessment
Country Code	ISO country identifier	International validation

Implementation Methods #

Real-Time API Integration #

Validate phone numbers as they enter your system. Best for: Form submissions, CRM imports, lead capture. See API integration guides.

Bulk Upload #

Upload CSV files for batch phone number validation. Results delivered within minutes. Best for: Database cleaning, inherited contact lists, quarterly hygiene.

Line Types Identified #

Trestle’s Phone Validation API identifies seven unique line types:

1. Mobile: Cell phone numbers
2. Landline: Traditional phone lines
3. Fixed VoIP: VoIP numbers associated with physical addresses
4. Non-Fixed VoIP: Virtual numbers (Google Voice, Viber, Textfree)
5. Toll-Free: 800/888/877 numbers
6. Premium: Pay-per-call services
7. Voicemail Service: Dedicated voicemail lines

Use Cases #

Lead Management

• Filter out disconnected numbers before calling
• Prioritize leads based on Phone Activity Scores
• Remove invalid numbers from marketing campaigns

Call Operations

• Reduce wasted agent time on bad numbers
• Route calls accordingly
• Optimize SMS delivery by line type distinction 

Data Quality

• Validate phone numbers at point of entry
• Maintain clean contact databases
• Identify fake or temporary numbers

Global Coverage #

Trestle validates phone numbers across 200+ countries and territories with coverage of 18,000+ global carriers from a database of 1B+ phone numbers.

Integration Best Practices #

• Validate at Entry: Implement real-time validation when phone numbers are submitted through forms, uploaded to CRM, or entered manually.
• Schedule Regular Cleaning: Re-validate existing contact databases on a regular schedule to catch numbers that have been disconnected since initial validation. We recommend validating your contact phone-database at least quarterly to stay ahead of the 18-25% annual decay rate, and more frequently if your list is large or high priority.
• Set Activity Score Thresholds: Define what Activity Score qualifies as “valid” for your business needs. Some operations may accept scores of 50+, others may require 70+.
• Handle Different Line Types: Determine whether your business accepts VoIP numbers, landlines only, or mobile-only contacts and filter accordingly.

Getting Started #

Trestle offers a 14-day free trial with 25 free validations. No credit card required and full access to all Phone Validation API features including Activity Scores, carrier lookup, line type detection, and prepaid status checks.

Frequently Asked Questions #

How does phone validation identify disconnected numbers?

Phone validation APIs query carrier databases and network signals to determine if a phone number is currently active and assigned to a subscriber. Trestle returns a Phone Activity Score from 0-100 indicating connection confidence.

What is the difference between phone validity and phone activity?

Phone validity confirms whether a phone number is correctly formatted, reachable, and capable of receiving calls or texts. Phone activity goes a step further by detecting recent behavioral signals, such as outbound or inbound activity, to indicate whether the number is actively being used

What is a Phone Activity Score?
A Phone Activity Score is a 0-100 rating that indicates phone activity volume. Scores of 70+ indicate high confidence the phone is connected, while scores of 30 or below indicate high confidence the phone is disconnected.

Can I validate phone numbers in bulk?
Yes. Trestle supports both real-time API validation and bulk CSV upload for database cleaning and large-volume validation needs. For more information, see Bulk Validation.

What phone number formats are accepted?
The API accepts E.164 format (+country code + number) and can parse local formats when country code parameters are provided. See Acceptable Phone Number Formats to learn more.

Does phone validation work internationally?
Yes. Trestle validates phone numbers across 200+ countries with coverage of 18,000+ global carriers.

How quickly does the API respond?
The API returns validation results in real-time, enabling immediate filtering of disconnected numbers without impacting user experience.