Should I obey my parents or not, since they do not allow me to raise my garment?

Allah has commanded kindness and good treatment towards parents, and obedience to them is obligatory unless they command disobedience. Trailing the garment below the ankles (Isbal) is one of the major sins, so there is no obedience to them if they command it. Do not disobey Allah for their sake. You can raise the garment so that it does not touch the ankles, thereby neither disobeying your Lord nor contradicting your parents' wish. It is not a condition for it to be halfway up the calf. If they insist on lengthening the garment, then be gentle with them, but Isbal remains forbidden and one of the major sins.