II.4.7  The contractor must ensure that the  personnel performing the contract and any future  replacement  personnel possess the professional qualifications and experience required to  provide the services, as the case may be on the basis of the selection criteria set out in the  tender specifications.  II.4.8  At the contracting au thority’s reasoned request, the contractor must replace any member of  personnel  who:  (a) does not have the expertise required to provide the services; or  (b) has caused disruption at the premises of the contracting authority.  The contractor bears the cost of replacing its  personnel  and is responsible for any delay in  providing the services resulting from the replacement of  personnel .  II.4.9  The contractor must record and report to the contracting authority any problem that affects its  ability to provide the services. The report must describe the problem, state when it started and  what action the contractor is taking to resolve it. II.4.10 The contractor must immediately inform the Contracting authority of any changes in the  exclusion situations as declared, according to Article 137 (1) of Regulation (EU) 2018/1046.  II.5 COMMUNICATION BETWEEN THE PARTIES  II.5.1 Form and means of communication  Any communication of information, notices or documents under the contract must:  (a) be made in writing in paper or electronic format in the language of the contract; (b) bear the contract number;  (c) be made using the relevant communication details set out in Article I.8; and  (d) be sent by mail, email or, for the documents specified in the special conditions, via  e-PRIOR . If a party requests written confirmation of an e-mail within a reasonable time, the other party must  provide an original signed paper version of the communication as soon as possible.  The parties agree that any communication made by email has full legal effect and is admissible as  evidence in judicial proceedings.  Any communication is deemed to have been made when the receiving party receives it, unless this  contract refers to the date when the communication was sent.  E-mail is deemed to have been received by the receiving party on the day of dispatch of that e-mail,  provided that it is sent to the e-mail address indicated in Article I.8. The sending party must be able  to prove the date of dispatch. In the event that the sending party receives a non-delivery report, it  must make every effort to ensure that the other party actually receives the communication by email  or mail. In such a case, the sending party is not held in breach of its obligation to send such  communication within a specified deadline.  Mail sent to the contracting authority is deemed to have been received by the contracting authority  on the date on which the department responsible referred to in Article I.8 registers it.  II.5.2 Date of communications by mail and email  17 