Is there any error in the continued telephone communication between the questioner and her male colleague after he became injured and confined to a wheelchair, given their knowledge of his previous attempts to get close to her and her rejection of them?

Speaking with an unfamiliar young man is not permissible except out of necessity. Your necessity is removed by a single contact or by asking his female relatives. It is not permissible to continue speaking with him because scholars have been strict about this matter due to the likelihood of fitna (temptation/strife) therein. It is stated in Bariqa Mahmudiyya: "Speaking with an unfamiliar young woman is not permissible without necessity." Neither of you should respond to the other's sneeze with "Yarhamukallah" (May Allah have mercy on you), nor should you return greetings audibly, but only to yourselves. This is based on the Prophet's (peace be upon him) saying: "And the adultery of the tongue is speech." As for the permissibility of permissible speech with an unfamiliar woman, it is understood to be in cases of necessity, or when there is no fear of lust, or with an old woman from whom inclination has ceased.