Joint Obligations to Obligations with a Penal Clause

Five law students who were childhood best friends from the province, rented the apartment of Sara for a period of one year. However, the pandemic struck and all but one, Ramses, returned to the province. However, Ramses also needs to move from Manila to Pasig because he found employment there as a legal secretary, so he also bid goodbye to Sara. Sara discovered that there is an unpaid DSL bills totaling to an amount of P5,000. One day, Sara showed up at Ramses new workplace and demanded him to pay the entire unpaid DSL bills. Sara pointed out that lease contract provided that the lessees shall pay for the DSL services in the leased premises. Is Sara correct in demanding the entire DSL bills from Ramses?