diff --git a/.travis.yml b/.travis.yml
index 02ad7a8..98371d1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,13 +3,14 @@ language: php
 
 # Versions of PHP you want your project run with.
 php:
+  - 7.2
   - 7.3
   - 7.4
 
 # Commands to be run before your environment runs.
 before_script:
   - composer self-update
-  - composer install --prefer-source --no-interaction --dev
+  - composer install
 
 # Commands you want to run that will verify your build.
 script: phpunit
diff --git a/src/GsmDetector.php b/src/GsmDetector.php
index 8972c44..060ce2b 100644
--- a/src/GsmDetector.php
+++ b/src/GsmDetector.php
@@ -15,7 +15,9 @@ class GsmDetector
 
     private static $mobileKeyName = "mobile";
 
-    private static $telPrefixLength = 2;
+    private static $mobilePrefixLength = 2;
+
+    private static $fixPrefixLength = 3;
 
     /**
      * GsmDetector constructor.
@@ -83,9 +85,7 @@ public function isGsm($name, string $value)
 
         $prefix = call_user_func_array('array_merge', $gsmConfig);
 
-        $numberPrefix = $this->getNumberPrefix($value);
-
-        return in_array($numberPrefix, $prefix);
+        return $this->hasValue($prefix, $value);
     }
 
     /**
@@ -98,11 +98,9 @@ public function isGsmWithType($gsm, $type, $value)
     {
         $gsmConfig = self::$config[$gsm];
 
-        $typePrefix = $gsmConfig[$type];
-
-        $numberPrefix = $this->getNumberPrefix($value);
+        $prefix = $gsmConfig[$type];
 
-        return in_array($numberPrefix, $typePrefix);
+        return $this->hasValue($prefix, $value);
     }
 
     /**
@@ -129,15 +127,14 @@ private function gsmHasType($gsm, $type)
      */
     public function isType($value, $type)
     {
-        $typeArray = [];
+        $prefix = [];
 
-        $numberPrefix = $this->getNumberPrefix($value);
 
         foreach (self::$config as $config) {
-            $typeArray = array_merge($typeArray, $config[$type]);
+            $prefix = array_merge($prefix, $config[$type]);
         }
 
-        return in_array($numberPrefix, $typeArray);
+        return $this->hasValue($prefix, $value);
     }
 
     /**
@@ -146,12 +143,10 @@ public function isType($value, $type)
      */
     public function getGsmName($value)
     {
-        $numberPrefix = $this->getNumberPrefix($value);
-
         foreach (self::$config as $key => $config) {
             $prefix = call_user_func_array('array_merge', $config);
 
-            if (in_array($numberPrefix, $prefix)) {
+            if ($this->hasValue($prefix, $value)) {
                 return $key;
             }
         }
@@ -169,9 +164,14 @@ public static function setConfig(array $config)
         self::$config = $config;
     }
 
-    public static function setTelPrefixLength(int $length)
+    public static function setMobilePrefixLength(int $length)
+    {
+        self::$mobilePrefixLength = $length;
+    }
+
+    public static function setFixPrefixLength(int $length)
     {
-        self::$telPrefixLength = $length;
+        self::$fixPrefixLength = $length;
     }
 
     /**
@@ -213,8 +213,14 @@ private static function validateConfigFormat($config)
      * @param $value
      * @return false|string
      */
-    private function getNumberPrefix($value)
+    private function getNumberPrefix($value, $prefixLength)
+    {
+        return substr($value, 0, $prefixLength);
+    }
+
+    private function hasValue($prefix, $value)
     {
-        return substr($value, 0, self::$telPrefixLength);
+        return in_array($this->getNumberPrefix($value, self::$mobilePrefixLength), $prefix) ||
+            in_array($this->getNumberPrefix($value, self::$fixPrefixLength), $prefix);
     }
 }
diff --git a/tests/GsmDetectorTest.php b/tests/GsmDetectorTest.php
index 34f94e2..25e80c8 100644
--- a/tests/GsmDetectorTest.php
+++ b/tests/GsmDetectorTest.php
@@ -28,13 +28,17 @@ public function test_is_gsm()
         $this->assertTrue($gsmDetector->isGsm('orange', '35000000'));
         $this->assertFalse($gsmDetector->isGsm('togocel', '26000000'));
         $this->assertFalse($gsmDetector->isGsm('orange', '29000000'));
+
+        GsmDetector::setFixPrefixLength(3);
+
+        $this->assertFalse($gsmDetector->isGsm('orange', '215000000'));
     }
 
     public function test_is_gsm_with_type()
     {
         $gsmDetector = new GsmDetector([
             'orange' => [
-                'fix' => ['22', '35'],
+                'fix' => ['22', '35', '215'],
                 'mobile' => ['88', '87']
             ],
             'togocel' => [
@@ -49,13 +53,17 @@ public function test_is_gsm_with_type()
         $this->assertFalse($gsmDetector->isGsmWithType('orange', 'mobile', '35000000'));
         $this->assertFalse($gsmDetector->isGsmWithType('togocel', 'fix', '01000000'));
         $this->assertTrue($gsmDetector->isGsmWithType('orange','fix', '35000000'));
+
+        GsmDetector::setFixPrefixLength(3);
+
+        $this->assertTrue($gsmDetector->isGsmWithType('orange','fix', '21500000'));
     }
 
     public function test_is_gsm_name()
     {
         $gsmDetector = new GsmDetector([
             'orange' => [
-                'fix' => ['22', '35'],
+                'fix' => ['22', '35', '215'],
                 'mobile' => ['09', '88']
             ],
             'togocel' => [
@@ -72,6 +80,10 @@ public function test_is_gsm_name()
         $this->assertTrue($gsmDetector->isOrange('88000000'));
         $this->assertTrue($gsmDetector->isOrange('09000000'));
         $this->assertTrue($gsmDetector->isOrange('22000000'));
+
+        GsmDetector::setFixPrefixLength(3);
+
+        $this->assertTrue($gsmDetector->isOrange('21500000'));
     }
 
     public function test_is_gsm_name_with_type()