Some people who say they truly believe in God often seem to act rather as though they don't.
I agree with you Errol. As for taking away our free will, it takes away our choice to believe or not to believe because we know for a fact God exists but yes we can still determine our own actions but again that makes us heavily accountable for what we do. To give you an example of a story from the Quran about the disciples of Jesus.
[And remember] when the disciples said, "O Jesus, Son of Mary, can your Lord send down to us a table [spread with food] from the heaven? [Jesus] said," Fear Allah , if you should be believers."They said, "We wish to eat from it and to be stronger in our faith and know that you have been truthful to us and be among its witnesses." Jesus, the son of Mary said, "O Allah , our Lord, send down to us a table [spread with food] from the heaven to be for us a festival for the first of us and the last of us and a sign from You. And provide for us, and You are the best of providers." Allah said, "Indeed, I will sent it down to you, but whoever disbelieves afterwards from among you - then indeed will I punish him with a punishment by which I have not punished anyone among the worlds." (Chapter 5, verses 112-115)
Because they asked for an extraordinary miracle and were granted it they were now more accountable then others because of it. If they were to go back on their faith they would be punished more severely then someone who had not seen the miracle and so had some excuse for their doubt.
Just to reiterate:
'To understand the full context, verses before and after have to be also taken into consideration starting from verse 110 until verse 120. In verse 110, Allah starts with the great miracles that He favored Jesus (peace be upon him) with.
Many people expect miracles to believe; however, a true believer is able to see the truth without experiencing any miracles.
Note the Prophet Muhammad’s companions did not ask him for any miracles; it was only the disbelievers of Quraish (the Arab tribe of the Prophet Muhammed PBUH) who asked for miracles and when the Prophet (peace be upon him) showed them miracles that Allah favored him with, they still did not believe.
So here Jesus’s disciples saw great miracles from Allah, such as raising the dead, yet they dared asking for another miracle; therefore, the response of Jesus (peace be upon him) “Ittaqullah”, meaning “fear Allah” and translated in the above verses as “Observe your duty to Allah”.
Unfortunately the translation does not convey the proper appreciative meaning. This is an expression of blame, where Jesus is blaming his disciples for requesting such a miracle; therefore, the following statement “If you are true believers”.
Jesus (peace be upon him) feared the consequences of this trial upon his disciples and asked them to depend on Allah for their provision.
When the disciples insisted, Jesus (peace be upon him) supplicated to Allah to bring forth the miracle. However, Allah warned them that whosoever disbelieves, shall receive the most severe punishment.
So disbelieving after experiencing divine miracles is one of the worst sins since knowing by seeing is different than knowing by hearsay'.^