The debate is well-known as endless.
(i) there is only freewill;
(ii) there is only प्रारब्ध
Although I tilt more or less towards the latter, I could also be considered as part of a third group that accepts that:
(iii) circumstances are due to प्रारब्ध, while the way one responds to it is freewill.
Be that as it may, the journey, I think, is from the first through the third into the second. Why so? Without freewill, one would be no better than animals, but we indeed are different being endowed with a well-formed intellect. This intellect unused can still make one an animal, if dharma is lacking, so one has to use one's freewill to get over circumstances of choice of प्रेयस् and श्रेयस् presented due to प्रारब्ध। This is possible only if one chooses to study धर्मशास्त्र। One may misuse freewill otherwise and then remain in the first category. The reason this has to culminate in the second is quite simple. mokSha is the real पुरुषार्थ and whatever one chooses, unless one doesn't choose Atma, that freewill would have been used in vain. If one chooses Atma over anAtma, then everything else has to be dropped as प्रारब्ध। As Bhagavatpadacharya says प्रारब्धाय समर्पितं स्ववपुः। As long as one holds on to the freewill, one is a कर्ता, as defined by Maharshi Panini as स्वतन्त्रः कर्ता, one who is independent, holding onto one's individuality is कर्ता। This is a जीव who has कर्तृत्वभोक्तृत्वभाव, and thereby, a संसारी। The question that usually pops up then is who is the कर्ता। Panini Maharshi has been kind enough to clarify the same in the next sutra तत्प्रयोजको हेतुश्च। That Ishvara who is the facilitator of the individual is the real कर्ता, being the कर्मफलदाता, who is the cause of everything there is, and being in the form of everything that there is. Ergo, the only freewill one really has is to give up the freewill, dropping one's जीवत्व and remaining as सर्वात्मब्रह्म instead.
व्याकरणं मुखं प्रोक्तम्।