They don't change christianity as I am sure you will say is the case with islam. they simply teach false doctrine and error which Jesus told us would happen

>>>18 For they that are such serve not our Lord Jesus Christ, but their own belly; and by good words and fair speeches deceive the hearts of the simple.
Romans 16:18 (KJV)

>>>10 His watchmen are blind: they are all ignorant, they are all dumb dogs, they cannot bark; sleeping, lying down, loving to slumber. 11 Yea, they are greedy dogs which can never have enough, and they are shepherds that cannot understand: they all look to their own way, every one for his gain, from his quarter. 12 Come ye, say they, I will fetch wine, and we will fill ourselves with strong drink; and to morrow shall be as this day, and much more abundant.
Isaiah 56:10-12 (KJV)

>>>19 And will ye pollute me among my people for handfuls of barley and for pieces of bread, to slay the souls that should not die, and to save the souls alive that should not live, by your lying to my people that hear your lies?
Ezek 13:19 (KJV)

>>>3 Knowing this first, that there shall come in the last days scoffers, walking after their own lusts,
2 Peter 3:3 (KJV)

>>>15 Beware of false prophets, which come to you in sheep's clothing, but inwardly they are ravening wolves.
Matt 7:15 (KJV)

>>>17 Now I beseech you, brethren, mark them which cause divisions and offences contrary to the doctrine which ye have learned; and avoid them.
Romans 16:17 (KJV)

>>>3 If any man teach otherwise, and consent not to wholesome words, even the words of our Lord Jesus Christ, and to the doctrine which is according to godliness;
1 Tim 6:2-3 (KJV)

>>>3 For the time will come when they will not endure sound doctrine; but after their own lusts shall they heap to themselves teachers, having itching ears;
2 Tim 4:2-3 (KJV)........