Praise be to Allah.
Firstly: the ruling on using company property for personal interests.
The basic principle is that company phones should not be used except for company interests, and the mobile phone and its credit are a trust held by the employee, so he should not use it except with permission, because of the general meaning of the verse (interpretation of the meaning):
“O you who have believed, do not consume one another's wealth unjustly but only [in lawful] business by mutual consent” [an-Nisa’ 4:29].
And the Prophet (blessings and peace of Allah be upon him) said: “Your blood, your wealth and your honour are sacred to you, as sacred as this day of yours, in this month of yours, in this land of yours. Let those who are present convey it to those who are absent.” Narrated by al-Bukhaari (67) and Muslim (1679).
And he (blessings and peace of Allah be upon him) said: “It is not permissible to take a person’s property unless he gives it willingly.” Narrated by Ahmad (20127); classed as saheeh by al-Albaani in Irwa’ al-Ghaleel (1459).
If the employee is given the balance as a gift, and it is stipulated that he should use it for particular calls, then he must comply and limit himself to that, so how about if it is given to him to use for work purposes only?
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: The basic principle in our view concerning this matter is that if someone takes any person’s property for a specific purpose, then he should not dispose of it for any other purpose except after asking their permission. End quote from al-Liqa’ ash-Sharhi (4/9).
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was asked: What is the ruling on an employee using some small items of government property in the office for personal benefit, such as pens, envelopes, rulers and the like? May Allah reward you with good.
Using government property that may be in the office for personal matters is haraam, because it is contrary to the trust that Allah has enjoined us to uphold.
That applies except in cases where what you do will not cause any harm, such as using a ruler, because that does not affect anything or do any harm. As for using pens, paper and cameras, using them for personal matters when they belong to the government is not permissible.
End quote from Fataawa Islamiyyah (4/306).
For more information, please see the answer to question no. 99394.
Secondly: the ruling on using extra phone credit that is surplus to company needs and free credit
With regard to extra phone credit that is surplus to company needs, or free phone credit, if it will be cancelled after that and no one will make use of it in the interests of the company, then what appears to be the case is that the employee’s making use of it is better than it being wasted without any benefit or compensation that could benefit the company. The Prophet (blessings and peace of Allah be upon him) forbade wasting money, and the additional credit that is not needed for company interests, and that the company has no plans to make use of, will be wasted.
It says in Fataawa al-Lajnah ad-Daa’imah (15/391): Question: sometimes when I am at work, I take some of the things that we use at work, such as photocopy paper, or used typewriter ribbons, or pens, or carbon copy, for personal use or to give to a friend. Sometimes I ask the boss for permission and he gives me permission to take it, and sometimes he does not give me permission and I take it without his knowledge. It is taking it haraam, whether with the boss’s permission or without it? Please note that these things do not belong to the boss or to any individual in the company. If there are things that are going to be thrown in the trash and I take them, is there any sin on me? I hope that you will advise me, may Allah reward you.
Answer: it is not permissible for the employee or worker to use equipment or other things belonging to the company or the management for personal purposes, because that is a transgression against the rights of others, without their permission. The Prophet (blessings and peace of Allah be upon him) said: “It is not permissible to take the property of a Muslim unless he gives it willingly.”
If there are things that are going to be thrown in the trash, then there is nothing wrong with taking them, because the owners have abandoned them.
And Allah is the source of strength. May Allah send blessings and peace upon our Prophet Muhammad and his family and companions.
Permanent Committee for Academic Research and Ifta’
Bakr Abu Zayd, ‘Abd al-‘Azeez Aal ash-Shaykh, Saalih al-Fawzaan, ‘Abdullah ibn Ghadyaan, ‘Abd ar-Razzaaq ‘Afeefi, ‘Abd al-‘Azeez ibn ‘Abdullah ibn Baaz. End quote.
If it is possible to ask permission from the company or the manager who is responsible for that, that is better and is more prudent, whatever the case.
And Allah knows best