You only have two option, Virtual University and Allama Iqbal Open University. And while these two universities offer similar services, they couldn't be any more different.
AIOU is completely analogue and their system hasn't seen any sort of improvement since the 70s. You apply for a semester via the traditional way (Buy prospectus, fill bank challan, so on), they send you books with assignment leaflets and then you'll have to make assignments with pen and paper (Digital i.e printed assignments are not allowed!) and submit them either in person or via registered mail before the designated last date of submission. Keep in mind that the assignments are compulsory and if you fail to submit your assignments within the allocated time period; you won't receive your roll number slip and won't be eligible to sit in the examination room.
VU is the polar opposite of AIOU. Everything and I mean EVERYTHING is digital and online, including assignments, exams, tutors, lectures etc. They do publish course books; but they are not compulsory as their lectures tend to be very intensive and through and you can rely on them 100%, but it's all up to you. Needless to say; you must have good English speaking skills, good typing speed and extensive knowledge of MS Word, Powerpoint and MathType programs etc, if you want to go down that route.
Hope it helps.